Smoke billowing from nuclear plant

Grey smoke rises from Unit 3 of the tsunami-stricken Fukushima Dai-ichi nuclear power plant in Japan (AP)

Sumi Abe, 80, is rescued from her destroyed home in Ishinomaki, Japan (AP)

Fukushima nuclear plant

A helicopter rescues two survivors, an 80-year-old woman and her teenage grandson (AP)

An 80-year-old woman is carried on a stretcher to the Ishinomaki Red Cross Hospital after being rescued with a 16-year-old boy

Damage following an earthquake and tsunami to the Fukushima Dai-ichi nuclear power plant in Japan (AP)

The damaged Fukushima Dai-ichi nuclear power plant in Japan (AP)

The evacuation of Britons from Japan is gathering pace (AP)

Rescue workers search for quake and tsunami victims at a beach in Kesennuma, northeastern Japan (AP)

Smoke rises from the No 3 unit at the Fukushima Dai-ichi nuclear complex in Okumamachi, north-eastern Japan (AP)

Thick while smoke billows from the No 3 unit of the Fukushima Dai-ichi nuclear power plant in Japan (AP/Tokyo Electric Power)

Thousands queue to get on flights at Narita International airport to evacuate Japan (AP)

Helicopters scoop water off Japan's north-east coast on their way to the stricken Fukushima Dai-ichi nuclear power plant (AP)

A man cycles past a wrecked car following the earthquake triggered tsunami at the port in Sendai, Japan (AP)

Reiko Miura, 68, cries as she looks for her sister's son at a tsunami-hit area in Otsuchi, northern Japan

Yoshikatsu Hiratsuka grieves in front of wreckage where the body of his mother is buried in Onagawa, northern Japan Thursday, March 17

A baby is checked for radiation exposure level in Nihonmatsu in Fukushima prefecture (state) Tuesday, March 15, 2011 following a third explosion at the Fukushima Dai-ichi nuclear power complex Tuesday, March 15, 2011

A radiation detector is used near Shibuya train station in Tokyo

Pharmacist Donna Barsky measures potassium iodide for a prescription at the Texas Star Pharmacy on Tuesday, March 15, 2011 in Plano, Texas. The pharmacy has been receiving an unusually high number of calls about potassium iodide from people who are afraid radiation from the Japan nuclear crisis will reach the U.S. Health agencies in California and western Canada warned Tuesday that there's no reason for people an ocean away to suddenly stock up on potassium iodide, even as some key suppliers say they're back-ordered and getting panicked calls from would-be customers. (AP Photo/Richard Matthews)

Debris is seen through an area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two". (Photo by Kiyoshi Ota/Getty Images)

Members of a Korean rescue team walk through an area damaged by earthquake and tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two".

Local residents walk through an area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two"

A local resident clears up in the area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two".

A clock that appears to indicate the time when a tsunami struck lies among the rubble in the city of Kesennuma, northeastern Japan, on Tuesday March 15, 2011. The Japanese characters read: "40th Anniversary of Foundation."

An official wearing a protective suit helps usher people through a radiation emergency scanning center in Koriyama, Japan, Tuesday, March 15, 2011, four days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

The damaged Fukushima Dai-ichi nuclear facility in Japan (AP)

Rescuers continue to pull survivors from the rubble following the earthquake in Japan (AP)

Smoke rises from the Fukushima Dai-ichi nuclear plant's Unit 3 (AP)

Upon hearing another tsunami warning, a father tries to flee for safety with his just reunited four-month-old baby girl who was spotted by Japan's Self-Defense Force member in the rubble of tsunami-torn Ishinomaki Monday, March 14, 2011, three days after a powerful earthquake-triggered tsunami hit northeast Japan.

The damaged Fukushima Dai-ichi nuclear facility in Japan (AP)

Workers remove the rubble in the earthquake and flood het area Monday, March 14, 2011 in Kesennuma, northern Japan following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

Vehicles are left on a flooded street in Watari, Miyagi, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

Firefighters and rescuers conduct their operations in Watari, Miyagi, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

Rescue workers run through rubble for the higher place in Rikuzentakata in Iwate Prefecture, northeastern Japan, upon hearing a tsunami warning Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/The Yumiuri Shimbun) JAPAN OUT, CREDIT MANDATORY

Damaged platforms for bullet trains are seen in Sendai, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

Japan's Chief Cabinet Secretary Yukio Edano speaks during a press conference about planned blackouts in Tokyo and other cities, and the second hydrogen explosion at Dai-ichi nuclear plant, in Tokyo Monday, March 14, 2011. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

This Nov. 15, 2009 photo provided by GeoEye shows the Fukushima Dai-ichi nuclear complex in Japan. An 8.9-magnitude earthquake struck Japan on March 11, 2011, causing a tsunami that devastated the region. Four nuclear plants in northeastern Japan have reported damage, but the danger Monday appeared to be greatest at the Fukushima Dai-ichi complex, where one explosion occurred over the weekend and a second was feared. (AP Photo/GeoEye) MANDATORY CREDIT, NO SALES

In this March 12, 2011 photo provided by the U.S. Navy, an SH-60B helicopter assigned to the Chargers of Helicopter Antisubmarine Squadron (HS) 14 from Naval Air Facility Atsugi flies over the city of Sendai, Japan to deliver more than 1,500 pounds of food to survivors of an 8.9 magnitude earthquake and a tsunami. The citizens of Ebina City, Japan, donated the food, and HS-14 is supporting earthquake and tsunami relief operations in Japan as directed. (AP Photo/U.S. Navy)

Residents head to search for missing people in Yamada, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

Smoke rise from an oil refinery on fire following a tsunami triggered by a strong earthquake in Tagajo, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011. (AP Photo/Koji Sasahara)

A helicopter from fire department searches over the debris of a destroyed house Monday, March 14, 2011 in Yamamoto, Miyagi Prefecture, Japan following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

The No. 1 reactor of the Fukushima Daiichi Nuclear Power Plant, is seen at left, with its upper part of the walls blown off after an explosion in Okumamachi, Fukushima Prefecture (state), northeastern Japan, Saturday, March 12, 2011. (AP Photo/Mainichi Shimbun, Taichi Kaizuka) JAPAN OUT NO SALES ONLINE OUT MANDATORY CREDIT

Rubble is scattered across the wide areas of the town of Minami Sanriku, northeastern Japan, on Sunday March 13, 2011, two days after a powerful earthquake and tsunami hit the the country's northeastern coast. (AP Photo/Kyodo News) MANDATORY CREDIT, NO LICENSING ALLOWED IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

A man holds his baby as they are scanned for levels of radiation in Koriyama, Fukushima Prefecture, Japan, Sunday, March 13, 2011. Friday's quake and tsunami damaged two nuclear reactors at a power plant in the prefecture, and at least one of them appeared to be going through a partial meltdown, raising fears of a radiation leak. (AP Photo/Mark Baker)

A man climbs out the window of his heavily damaged home Monday, March 14, 2011, in Yotsukura, Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)

A woman walks past a damaged car Moday, March 14, 2011, in Yotsukura, Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)

A man, with his face covered to protect against dust, looks out at the damage Monday, March 14, 2011, in Yotsukura, Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)

A residents of the seaside town of Yotsukura, northern Japan, walks past damaged homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

A resident of the seaside town of Yotsukura, northern Japan, carries his bike through debris Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

Residents of the seaside town of Yotsukura, northern Japan, inspect under their car as they clear debris from their homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

A resident of the seaside town of Yotsukura, northern Japan, clears debris from his home Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

ALTERNATE CROP AND CAPTION ADDITION - A mother strokes the head of her dead daughter as she and her husband look at the body of their daughter they found in a courtesy vehicle of a driving school that's smashed by a tsunami at Yamamoto, northeastern Japan, on Saturday March 12, 2011, a day after a giant earthquake and tsunami struck the country's northeastern coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

This combo made from images provided by GeoEye shows an area of Natori, Japan on April 4, 2010, left, and March 12, 2011, after an 8.9-magnitude earthquake struck causing a tsunami that devastated the region. (AP Photo/GeoEye) MANDATORY CREDIT, NO SALES.

A parent and child react as they search for missing relatives through debris caused by Friday's massive earthquake and the ensuing tsunami, in Kamaishi, northern Japan Sunday, March 13, 2011. (AP Photo/Asahi Shimbun, Toshiyuki Hayashi) JAPAN OUT, NO SALES, MANDATORY CREDIT

People walk to receive water supply through a street with the rubble Monday March 14, 2011 in Kesennuma, Miyagi Prefecture, northern Japan following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

A fishing boat sits inland in Kesennuma, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

Members of Japan Self-Defense Forces rescue people stranded at a flooded city center in Ishinomaki, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

No. 3 unit of the Fukushima Daiichi Nuclear Power Plant, is seen, 2nd from right, with unit 1 reactor, left, with its top part of walls blown off after Saturday's explosion seen in Okumamachi, Fukushima Prefecture (state) , northern Japan Monday, March 14, 2011. Japanese officials say they believe a hydrogen explosion has occurred at the nuclear plant, similar to an earlier one at a different unit in the facility. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

People put away cans containing beer and juice swept out from a beer factory in Sendai, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake and tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

People walk amid the rubble in Rikuzentakata, Iwate prefecture, northern Japan, Sunday, March 13, 2011, two days after the powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

A man walks amid the rubble in Minamisanriku town, Iwate prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake and tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

This Arpil 4, 2010 image released by GeoEye shows an area of Ishinomaki, Japan. An 8.9-magnitude earthquake struck Japan on March 11, 2011, causing a tsunami that devastated the region. (AP Photo/GeoEye) SEE NY231 FOR SIMILAR IMAGE AFTER EARTHQUAKE. MANDATORY CREDIT, NO SALES.

A man watches a coastal area from a building where he took shelter in Tamura, Iwate, northern Japan as tsunami warning was issued Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

A car sits on top of a small building in a destroyed neighborhood in Sendai, Japan, on Sunday, March 13, 2011 after it was washed into the area by the tsunami that hit northeastern Japan. AP Photo/David Guttenfelder)

Young residents of the seaside town of Toyoma, northern Japan, walk amongst the debris around their homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

EDS NOTE: GRAPHIC CONTENT - The hand of a man killed sits among concrete sea barriers Monday, March 14, 2011, in Toyoma, northern Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)

A statue is all that remains of a house in the seaside town of Toyoma, northern Japan, Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

Residents of the seaside town of Toyoma, northern Japan, carry belongings from their homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)

This image made from Japan's NHK public television via Kyodo News shows the Fukushima Dai-ichi power plant's Unit 3 after an explosion Monday morning, March 14, 2011, in Okumamachi, Fukushima prefecture, northeastern Japan. Japan's chief cabinet secretary said a hydrogen explosion has occurred at Unit 3. The blast was similar to an earlier one at a different unit of the facility. (AP Photo/NHK TV via Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES, TV OUT, EDITORIAL USE ONLY, NO SALE IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

Police officers from Hyogo Prefecture search missing persons in the rubble in Kamaishi, Iwate Prefecture, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

CORRECTS WHOLE CAPTION - Patients at a hospital wait to be evacuated without medicine and electricity in Otsuchi in Iwate Prefecture (state) Sunday, March 13, 2011, two days after a strong earthquake and tsunami hit northeastern Japan. (AP Photo/The Yomiuri Shimbun, Yasuhiro Takami) JAPAN OUT, CREDIT MANDATORY

A couple walk along the rubble at a residential area in Onagawa, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/The Yumiuri Shimbun) JAPAN OUT, CREDIT MANDATORY

Gutted vehicles and the rubble is seen in Kesennuma, Miyagi prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

In this 1999 file photo, Unit 3 reactor of the Fukushima Daiichi Nuclear Power Plant is seen in Okumamachi, Fukushima Prefecture. Japan's chief cabinet secretary says a hydrogen explosion has occurred at Unit 3 Monday, March 14, 2011. The blast was similar to an earlier one at a different unit of the facility. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE

People walk in the rubble in Minamisanriku town, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/The Yumiuri Shimbun) JAPAN OUT, CREDIT MANDATORY

SHIROISHI, JAPAN - MARCH 13, 2011: (EDITORS NOTE: Image has been reviewed by U.S. Military prior to transmission.) In this handout image provided by U.S. Navy, sailors assigned to the Chargers of Helicopter Anti-submarine Squadron (HS-14) deliver 1,500 pounds of food on March 13, 2011 to residents of Shiroishi City in the Miyagi Prefecture, Japan. The citizens of Ebina City, Japan, donated the food, and HS-14 is providing humanitarian assistance in support of earthquake and tsunami relief operations in Japan as directed. An earthquake measuring 8.9 on the Richter scale has hit the northeast coast of Japan causing tsunami alerts throughout countries bordering the Pacific Ocean. (Photo by Oscar Sosa/U.S. Navy via Getty Images)

SENDAI, JAPAN - MARCH 14: A local resident tries to approach a car left abandoned in the area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)

SENDAI, JAPAN - MARCH 14: A worker operates a power shovel to remove trees after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)

SENDAI, JAPAN - MARCH 14: Members of the Ground Self-Defense Forces help a man evacuate the area when a warning of tsunami is issued after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)

SENDAI, JAPAN - MARCH 14: Members of a rescue team climb into a house after a warning of tsunami is issued after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)

SENDAI, JAPAN - MARCH 14: A local resident rests as she evacuates an area after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)

SENDAI, JAPAN - MARCH 14: Members of the Ground Self-Defense Forces help a man evacuate the area when a warning of tsunami is issued after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)

SENDAI, JAPAN - MARCH 14: Local residents walk through an area damaged by a tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)

ALTERNATE CROP OF TOK890 OF MARCH 13, 2011 - Futaba Kosei Hospital patients are assisted by Japan Self Defense Force personnel as they disembark from a helicopter in the compound of Fukushima Gender Equality Centre in Nihonmatsu, Fukushima Prefecture, northeastern Japan, Sunday morning, March 13, 2011 after being evacuated from the hospital in Futaba town near the troubled Fukushima Dai-ichi nuclear complex. They might have been exposed to radiation while waiting for evacuation when an explosion of Unit 1 reactor of the complex blew off the top part of its walls on Saturday, one day after a strong earthquake and tsunami hit northeastern Japan. (AP Photo/The Yomiuri Shimbun, Daisuke Tomita) JAPAN OUT, CREDIT MANDATORY

Boy carries bottles of water amid debris in Kesennuma, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE, CORRECTS DATE PHOTO TAKEN

In this video image taken from NTV Japan via APTN, smoke rises from Unit 1 of Fukushima Daiichi nuclear power plant in Okumamachi, Fukushima prefecture, Japan, Saturday, March 12, 2011. Government spokesman Yukio Edano said the explosion destroyed the exterior walls of the building where the reactor is placed, but not the metal housing enveloping the nuclear reactor, however the government has ordered the evacuation of all people within a 12-miles radius of the plant

A car leans against a wire from an electric pole in Miyako, northeastern Japan, Saturday, March 12, 2011, one day after an 8.9-magnitude quake and the tsunami it spawned hit the country's northeastern coast

White smokes rise from still burning house in Yamadamachi in Iwate Prefecture (state), northern Japan, Saturday, March 12, 2011, one day after a strong earthquake-triggered devastating tsunami hit the area

An elderly man is carried by a Self-Defense Force member in the tsunami-torn Natori city, Miyagi Prefecture, northern Japan, Saturday morning, March 12, 2011, one day after strong earthquakes hit the area

Houses are in flames while the Natori river is flooded over the surrounding area by tsunami tidal waves in Natori city, Miyagi Prefecture, northern Japan, March 11, 2011, after strong earthquakes hit the area

In this image made from Japan's NHK television, a house is sticks out from scattered debris as the area is submerged in Minami Soma, Fukushima prefecture (state), Friday, March 11, 2011 after a ferocious tsunami unleashed by Japan's biggest recorded earthquake slammed into its eastern coasts

A bride and groom from Japan walk in the lobby of the Sheration Waikiki Hotel, Friday, March 11, 2011 in Honolulu. A ferocious tsunami unleashed by Japan's biggest recorded earthquake slammed into its eastern coast Friday, killing hundreds of people as it carried away ships, cars and homes, and triggered widespread fires that burned out of control. Hours later, the waves washed ashore on Hawaii and the U.S. West coast, where evacuations were ordered from California to Washington but little damage was reported

An aerial view shows residential area affected by tsunami in Sendai, northern Japan Saturday, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday

SAN FRANCISCO - MARCH 11: (L - R) Leighana Murphy and Ted Lanpher walk across a portion of a beach between tsunami surges on March 11, 2011 in Half Moon Bay, California. A tsunami warning for Northern California has been issued and a voluntary evacuation is in effect in Half Moon Bay. (Photo by Kim White/Getty Images)

Black smoke raises from a building during a fire in Tokyo after one of the largest earthquakes on record slammed Japan's eastern coasts Friday, March 11, 2011

Houses are in flames while the Natori river is flooded over the surrounding area by tsunami tidal waves in Natori city, Miyagi Prefecture, northern Japan, March 11, 2011, after strong earthquakes hit the area

Smoke rises from burning facilities in an industrial zone in Tagajo, Miyagi Prefecture, Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Frida

Gas storage facilities burn in Tagajo, Miyagi Prefecture, Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday

Black smoke rises from burning buildings in a factory zone in Sendai, Miyagi Prefecture, Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday

A local resident walks through debris in Rikuzentakata, Iwate, northern Japan Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday

thumbnail: Grey smoke rises from Unit 3 of the tsunami-stricken Fukushima Dai-ichi nuclear power plant in Japan (AP)
thumbnail: Sumi Abe, 80, is rescued from her destroyed home in Ishinomaki, Japan (AP)
thumbnail: Fukushima nuclear plant
thumbnail: A helicopter rescues two survivors, an 80-year-old woman and her teenage grandson (AP)
thumbnail: An 80-year-old woman is carried on a stretcher to the Ishinomaki Red Cross Hospital after being rescued with a 16-year-old boy
thumbnail: Damage following an earthquake and tsunami to the Fukushima Dai-ichi nuclear power plant in Japan (AP)
thumbnail: The damaged Fukushima Dai-ichi nuclear power plant in Japan (AP)
thumbnail: The evacuation of Britons from Japan is gathering pace (AP)
thumbnail: Rescue workers search for quake and tsunami victims at a beach in Kesennuma, northeastern Japan (AP)
thumbnail: Smoke rises from the No 3 unit at the Fukushima Dai-ichi nuclear complex in Okumamachi, north-eastern Japan (AP)
thumbnail: Thick while smoke billows from the No 3 unit of the Fukushima Dai-ichi nuclear power plant in Japan (AP/Tokyo Electric Power)
thumbnail: Thousands queue to get on flights at Narita International airport to evacuate Japan (AP)
thumbnail: Helicopters scoop water off Japan's north-east coast on their way to the stricken Fukushima Dai-ichi nuclear power plant (AP)
thumbnail: A man cycles past a wrecked car following the earthquake triggered tsunami at the port in Sendai, Japan (AP)
thumbnail: Reiko Miura, 68, cries as she looks for her sister's son at a tsunami-hit area in Otsuchi, northern Japan
thumbnail: Yoshikatsu Hiratsuka grieves in front of wreckage where the body of his mother is buried in Onagawa, northern Japan Thursday, March 17
thumbnail: A baby is checked for radiation exposure level in Nihonmatsu in Fukushima prefecture (state) Tuesday, March 15, 2011 following a third explosion at the Fukushima Dai-ichi nuclear power complex Tuesday, March 15, 2011
thumbnail: A radiation detector is used near Shibuya train station in Tokyo
thumbnail: Pharmacist Donna Barsky measures potassium iodide for a prescription at the Texas Star Pharmacy on Tuesday, March 15, 2011 in Plano, Texas. The pharmacy has been receiving an unusually high number of calls about potassium iodide from people who are afraid radiation from the Japan nuclear crisis will reach the U.S. Health agencies in California and western Canada warned Tuesday that there's no reason for people an ocean away to suddenly stock up on potassium iodide, even as some key suppliers say they're back-ordered and getting panicked calls from would-be customers. (AP Photo/Richard Matthews)
thumbnail: Debris is seen through an area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two". (Photo by Kiyoshi Ota/Getty Images)
thumbnail: Members of a Korean rescue team walk through an area damaged by earthquake and tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two".
thumbnail: Local residents walk through an area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two"
thumbnail: A local resident clears up in the area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 15, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll continues to rise with fears that the official death count could well reach up to 10,000 in "the most tragic event in Japanese history since World War Two".
thumbnail: A clock that appears to indicate the time when a tsunami struck lies among the rubble in the city of Kesennuma, northeastern Japan, on Tuesday March 15, 2011. The Japanese characters read: "40th Anniversary of Foundation."
thumbnail: An official wearing a protective suit helps usher people through a radiation emergency scanning center in Koriyama, Japan, Tuesday, March 15, 2011, four days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: The damaged Fukushima Dai-ichi nuclear facility in Japan (AP)
thumbnail: Rescuers continue to pull survivors from the rubble following the earthquake in Japan (AP)
thumbnail: Smoke rises from the Fukushima Dai-ichi nuclear plant's Unit 3 (AP)
thumbnail: Upon hearing another tsunami warning, a father tries to flee for safety with his just reunited four-month-old baby girl who was spotted by Japan's Self-Defense Force member in the rubble of tsunami-torn Ishinomaki Monday, March 14, 2011, three days after a powerful earthquake-triggered tsunami hit northeast Japan.
thumbnail: The damaged Fukushima Dai-ichi nuclear facility in Japan (AP)
thumbnail: Workers remove the rubble in the earthquake and flood het area Monday, March 14, 2011 in Kesennuma, northern Japan following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: Vehicles are left on a flooded street in Watari, Miyagi, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: Firefighters and rescuers conduct their operations in Watari, Miyagi, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: Rescue workers run through rubble for the higher place in Rikuzentakata in Iwate Prefecture, northeastern Japan, upon hearing a tsunami warning Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/The Yumiuri Shimbun) JAPAN OUT, CREDIT MANDATORY
thumbnail: Damaged platforms for bullet trains are seen in Sendai, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: Japan's Chief Cabinet Secretary Yukio Edano speaks during a press conference about planned blackouts in Tokyo and other cities, and the second hydrogen explosion at Dai-ichi nuclear plant, in Tokyo Monday, March 14, 2011. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: This Nov. 15, 2009 photo provided by GeoEye shows the Fukushima Dai-ichi nuclear complex in Japan. An 8.9-magnitude earthquake struck Japan on March 11, 2011, causing a tsunami that devastated the region. Four nuclear plants in northeastern Japan have reported damage, but the danger Monday appeared to be greatest at the Fukushima Dai-ichi complex, where one explosion occurred over the weekend and a second was feared. (AP Photo/GeoEye) MANDATORY CREDIT, NO SALES
thumbnail: In this March 12, 2011 photo provided by the U.S. Navy, an SH-60B helicopter assigned to the Chargers of Helicopter Antisubmarine Squadron (HS) 14 from Naval Air Facility Atsugi flies over the city of Sendai, Japan to deliver more than 1,500 pounds of food to survivors of an 8.9 magnitude earthquake and a tsunami. The citizens of Ebina City, Japan, donated the food, and HS-14 is supporting earthquake and tsunami relief operations in Japan as directed. (AP Photo/U.S. Navy)
thumbnail: Residents head to search for missing people in Yamada, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: Smoke rise from an oil refinery on fire following a tsunami triggered by a strong earthquake in Tagajo, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011. (AP Photo/Koji Sasahara)
thumbnail: A helicopter from fire department searches over the debris of a destroyed house Monday, March 14, 2011 in Yamamoto, Miyagi Prefecture, Japan following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: The No. 1 reactor of the Fukushima Daiichi Nuclear Power Plant, is seen at left, with its upper part of the walls blown off after an explosion in Okumamachi, Fukushima Prefecture (state), northeastern Japan, Saturday, March 12, 2011. (AP Photo/Mainichi Shimbun, Taichi Kaizuka) JAPAN OUT NO SALES ONLINE OUT MANDATORY CREDIT
thumbnail: Rubble is scattered across the wide areas of the town of Minami Sanriku, northeastern Japan, on Sunday March 13, 2011, two days after a powerful earthquake and tsunami hit the the country's northeastern coast. (AP Photo/Kyodo News) MANDATORY CREDIT, NO LICENSING ALLOWED IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: A man holds his baby as they are scanned for levels of radiation in Koriyama, Fukushima Prefecture, Japan, Sunday, March 13, 2011. Friday's quake and tsunami damaged two nuclear reactors at a power plant in the prefecture, and at least one of them appeared to be going through a partial meltdown, raising fears of a radiation leak. (AP Photo/Mark Baker)
thumbnail: A man climbs out the window of his heavily damaged home Monday, March 14, 2011, in Yotsukura, Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)
thumbnail: A woman walks past a damaged car Moday, March 14, 2011, in Yotsukura, Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)
thumbnail: A man, with his face covered to protect against dust, looks out at the damage Monday, March 14, 2011, in Yotsukura, Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)
thumbnail: A residents of the seaside town of Yotsukura, northern Japan, walks past damaged homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: A resident of the seaside town of Yotsukura, northern Japan, carries his bike through debris Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: Residents of the seaside town of Yotsukura, northern Japan, inspect under their car as they clear debris from their homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: A resident of the seaside town of Yotsukura, northern Japan, clears debris from his home Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: ALTERNATE CROP AND CAPTION ADDITION - A mother strokes the head of her dead daughter as she and her husband look at the body of their daughter they found in a courtesy vehicle of a driving school that's smashed by a tsunami at Yamamoto, northeastern Japan, on Saturday March 12, 2011, a day after a giant earthquake and tsunami struck the country's northeastern coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: This combo made from images provided by GeoEye shows an area of Natori, Japan on April 4, 2010, left, and March 12, 2011, after an 8.9-magnitude earthquake struck causing a tsunami that devastated the region. (AP Photo/GeoEye) MANDATORY CREDIT, NO SALES.
thumbnail: A parent and child react as they search for missing relatives through debris caused by Friday's massive earthquake and the ensuing tsunami, in Kamaishi, northern Japan Sunday, March 13, 2011. (AP Photo/Asahi Shimbun, Toshiyuki Hayashi) JAPAN OUT, NO SALES, MANDATORY CREDIT
thumbnail: People walk to receive water supply through a street with the rubble Monday March 14, 2011 in Kesennuma, Miyagi Prefecture, northern Japan following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: A fishing boat sits inland in Kesennuma, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: Members of Japan Self-Defense Forces rescue people stranded at a flooded city center in Ishinomaki, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: No. 3 unit of the Fukushima Daiichi Nuclear Power Plant, is seen, 2nd from right, with unit 1 reactor, left, with its top part of walls blown off after Saturday's explosion seen in Okumamachi, Fukushima Prefecture (state) , northern Japan Monday, March 14, 2011. Japanese officials say they believe a hydrogen explosion has occurred at the nuclear plant, similar to an earlier one at a different unit in the facility. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: People put away cans containing beer and juice swept out from a beer factory in Sendai, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake and tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: People walk amid the rubble in Rikuzentakata, Iwate prefecture, northern Japan, Sunday, March 13, 2011, two days after the powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: A man walks amid the rubble in Minamisanriku town, Iwate prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake and tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: This Arpil 4, 2010 image released by GeoEye shows an area of Ishinomaki, Japan. An 8.9-magnitude earthquake struck Japan on March 11, 2011, causing a tsunami that devastated the region. (AP Photo/GeoEye) SEE NY231 FOR SIMILAR IMAGE AFTER EARTHQUAKE. MANDATORY CREDIT, NO SALES.
thumbnail: A man watches a coastal area from a building where he took shelter in Tamura, Iwate, northern Japan as tsunami warning was issued Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: A car sits on top of a small building in a destroyed neighborhood in Sendai, Japan, on Sunday, March 13, 2011 after it was washed into the area by the tsunami that hit northeastern Japan. AP Photo/David Guttenfelder)
thumbnail: Young residents of the seaside town of Toyoma, northern Japan, walk amongst the debris around their homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: EDS NOTE: GRAPHIC CONTENT - The hand of a man killed sits among concrete sea barriers Monday, March 14, 2011, in Toyoma, northern Japan, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Gregory Bull)
thumbnail: A statue is all that remains of a house in the seaside town of Toyoma, northern Japan, Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: Residents of the seaside town of Toyoma, northern Japan, carry belongings from their homes Monday, March 14, 2011, three days after a giant quake and tsunami struck the country's northeastern coast. (AP Photo/Mark Baker)
thumbnail: This image made from Japan's NHK public television via Kyodo News shows the Fukushima Dai-ichi power plant's Unit 3 after an explosion Monday morning, March 14, 2011, in Okumamachi, Fukushima prefecture, northeastern Japan. Japan's chief cabinet secretary said a hydrogen explosion has occurred at Unit 3. The blast was similar to an earlier one at a different unit of the facility. (AP Photo/NHK TV via Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES, TV OUT, EDITORIAL USE ONLY, NO SALE IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: Police officers from Hyogo Prefecture search missing persons in the rubble in Kamaishi, Iwate Prefecture, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: CORRECTS WHOLE CAPTION - Patients at a hospital wait to be evacuated without medicine and electricity in Otsuchi in Iwate Prefecture (state) Sunday, March 13, 2011, two days after a strong earthquake and tsunami hit northeastern Japan. (AP Photo/The Yomiuri Shimbun, Yasuhiro Takami) JAPAN OUT, CREDIT MANDATORY
thumbnail: A couple walk along the rubble at a residential area in Onagawa, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/The Yumiuri Shimbun) JAPAN OUT, CREDIT MANDATORY
thumbnail: Gutted vehicles and the rubble is seen in Kesennuma, Miyagi prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: In this 1999 file photo, Unit 3 reactor of the Fukushima Daiichi Nuclear Power Plant is seen in Okumamachi, Fukushima Prefecture. Japan's chief cabinet secretary says a hydrogen explosion has occurred at Unit 3 Monday, March 14, 2011. The blast was similar to an earlier one at a different unit of the facility. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE
thumbnail: People walk in the rubble in Minamisanriku town, Miyagi Prefecture, northern Japan, Sunday, March 13, 2011, two days after a powerful earthquake-triggered tsunami hit the country's east coast. (AP Photo/The Yumiuri Shimbun) JAPAN OUT, CREDIT MANDATORY
thumbnail: SHIROISHI, JAPAN - MARCH 13, 2011: (EDITORS NOTE: Image has been reviewed by U.S. Military prior to transmission.) In this handout image provided by U.S. Navy, sailors assigned to the Chargers of Helicopter Anti-submarine Squadron (HS-14) deliver 1,500 pounds of food on March 13, 2011 to residents of Shiroishi City in the Miyagi Prefecture, Japan. The citizens of Ebina City, Japan, donated the food, and HS-14 is providing humanitarian assistance in support of earthquake and tsunami relief operations in Japan as directed. An earthquake measuring 8.9 on the Richter scale has hit the northeast coast of Japan causing tsunami alerts throughout countries bordering the Pacific Ocean. (Photo by Oscar Sosa/U.S. Navy via Getty Images)
thumbnail: SENDAI, JAPAN - MARCH 14: A local resident tries to approach a car left abandoned in the area damaged by tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)
thumbnail: SENDAI, JAPAN - MARCH 14: A worker operates a power shovel to remove trees after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)
thumbnail: SENDAI, JAPAN - MARCH 14: Members of the Ground Self-Defense Forces help a man evacuate the area when a warning of tsunami is issued after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)
thumbnail: SENDAI, JAPAN - MARCH 14: Members of a rescue team climb into a house after a warning of tsunami is issued after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)
thumbnail: SENDAI, JAPAN - MARCH 14: A local resident rests as she evacuates an area after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)
thumbnail: SENDAI, JAPAN - MARCH 14: Members of the Ground Self-Defense Forces help a man evacuate the area when a warning of tsunami is issued after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)
thumbnail: SENDAI, JAPAN - MARCH 14: Local residents walk through an area damaged by a tsunami after a 9.0 magnitude strong earthquake struck on March 11 off the coast of north-eastern Japan, on March 14, 2011 in Sendai, Japan. The quake struck offshore at 2:46pm local time, triggering a tsunami wave of up to 10 metres which engulfed large parts of north-eastern Japan. The death toll is currently unknown, with fears that the current hundreds dead may well run into thousands. (Photo by Kiyoshi Ota/Getty Images)
thumbnail: ALTERNATE CROP OF TOK890 OF MARCH 13, 2011 - Futaba Kosei Hospital patients are assisted by Japan Self Defense Force personnel as they disembark from a helicopter in the compound of Fukushima Gender Equality Centre in Nihonmatsu, Fukushima Prefecture, northeastern Japan, Sunday morning, March 13, 2011 after being evacuated from the hospital in Futaba town near the troubled Fukushima Dai-ichi nuclear complex. They might have been exposed to radiation while waiting for evacuation when an explosion of Unit 1 reactor of the complex blew off the top part of its walls on Saturday, one day after a strong earthquake and tsunami hit northeastern Japan. (AP Photo/The Yomiuri Shimbun, Daisuke Tomita) JAPAN OUT, CREDIT MANDATORY
thumbnail: Boy carries bottles of water amid debris in Kesennuma, northern Japan Monday, March 14, 2011 following Friday's massive earthquake and the ensuing tsunami. (AP Photo/Kyodo News) JAPAN OUT, MANDATORY CREDIT, NO SALES IN CHINA, HONG KONG, JAPAN, SOUTH KOREA AND FRANCE, CORRECTS DATE PHOTO TAKEN
thumbnail: In this video image taken from NTV Japan via APTN, smoke rises from Unit 1 of Fukushima Daiichi nuclear power plant in Okumamachi, Fukushima prefecture, Japan, Saturday, March 12, 2011. Government spokesman Yukio Edano said the explosion destroyed the exterior walls of the building where the reactor is placed, but not the metal housing enveloping the nuclear reactor, however the government has ordered the evacuation of all people within a 12-miles radius of the plant
thumbnail: A car leans against a wire from an electric pole in Miyako, northeastern Japan, Saturday, March 12, 2011, one day after an 8.9-magnitude quake and the tsunami it spawned hit the country's northeastern coast
thumbnail: White smokes rise from still burning house in Yamadamachi in Iwate Prefecture (state), northern Japan, Saturday, March 12, 2011, one day after a strong earthquake-triggered devastating tsunami hit the area
thumbnail: An elderly man is carried by a Self-Defense Force member in the tsunami-torn Natori city, Miyagi Prefecture, northern Japan, Saturday morning, March 12, 2011, one day after strong earthquakes hit the area
thumbnail: Houses are in flames while the Natori river is flooded over the surrounding area by tsunami tidal waves in Natori city, Miyagi Prefecture, northern Japan, March 11, 2011, after strong earthquakes hit the area
thumbnail: In this image made from Japan's NHK television, a house is sticks out from scattered debris as the area is submerged in Minami Soma, Fukushima prefecture (state), Friday, March 11, 2011 after a ferocious tsunami unleashed by Japan's biggest recorded earthquake slammed into its eastern coasts
thumbnail: A bride and groom from Japan walk in the lobby of the Sheration Waikiki Hotel, Friday, March 11, 2011 in Honolulu. A ferocious tsunami unleashed by Japan's biggest recorded earthquake slammed into its eastern coast Friday, killing hundreds of people as it carried away ships, cars and homes, and triggered widespread fires that burned out of control. Hours later, the waves washed ashore on Hawaii and the U.S. West coast, where evacuations were ordered from California to Washington but little damage was reported
thumbnail: An aerial view shows residential area affected by tsunami in Sendai, northern Japan Saturday, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday
thumbnail: SAN FRANCISCO - MARCH 11: (L - R) Leighana Murphy and Ted Lanpher walk across a portion of a beach between tsunami surges on March 11, 2011 in Half Moon Bay, California. A tsunami warning for Northern California has been issued and a voluntary evacuation is in effect in Half Moon Bay. (Photo by Kim White/Getty Images)
thumbnail: Black smoke raises from a building during a fire in Tokyo after one of the largest earthquakes on record slammed Japan's eastern coasts Friday, March 11, 2011
thumbnail: Houses are in flames while the Natori river is flooded over the surrounding area by tsunami tidal waves in Natori city, Miyagi Prefecture, northern Japan, March 11, 2011, after strong earthquakes hit the area
thumbnail: Smoke rises from burning facilities in an industrial zone in Tagajo, Miyagi Prefecture, Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Frida
thumbnail: Gas storage facilities burn in Tagajo, Miyagi Prefecture, Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday
thumbnail: Black smoke rises from burning buildings in a factory zone in Sendai, Miyagi Prefecture, Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday
thumbnail: A local resident walks through debris in Rikuzentakata, Iwate, northern Japan Saturday morning, March 12, 2011 after Japan's biggest recorded earthquake slammed into its eastern coast Friday

Smoke is billowing from two of the damaged Japanese reactors, temporarily halting vital work to reconnect power lines and restore cooling systems to the complex.

Workers are racing to bring the nuclear plant under control, but the process is proceeding in fits and starts, hindered by incidents like the smoke and by the need to work methodically to make sure wiring, pumps and other machinery can be safely switched on.

What caused the smoke to billow first from Unit 3 at the Fukushima Dai-ichi plant and later from Unit 2 is under investigation. Workers were evacuated from the area to buildings nearby, though radiation levels remained steady, the officials said.

Traces of radiation are contaminating vegetables and some water supplies, although in amounts the government and health experts say do not pose a risk to human health in the short-term.

"Please do not overreact, and act calmly," said Chief Cabinet spokesman Yukio Edano. "Even if you eat contaminated vegetables several times, it will not harm your health at all."

He said Fukushima's operator, Tokyo Electric Power Company, would compensate farmers affected by bans on the sale of raw milk, spinach and canola cooking oil.

The Health Ministry advised people in Iitate, a village of 6,000 people about 19 miles from the plant, not to drink tap water due to raised levels of iodine.

The nuclear safety agency and Tokyo Electric have reported significant progress over the past few days, with electrical teams, having finished connecting three of the plant's six units, now working to connect the rest .

Once done, however, pumps and other equipment have to be checked - and the reactors cleared of dangerous gas - before the power can be restored.

Growing concerns about radiation add to the chain of disasters Japan has struggled with since the massive earthquake and resulting tsunami.