Huge blast at Japan nuclear power plant.

A massive explosion has rocked a Japanese nuclear power plant after Friday's devastating earthquake.
s show a blast at the Fukushima-Daiichi plant
A huge pall of smoke was seen coming from the plant at Fukushima and several workers were injured.

Japanese officials fear a meltdown at one of the plant's reactors but say the container housing it was not damaged.

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A huge relief operation is under way after the 8.9-magnitude earthquake and the tsunami it triggered, which is thought to have killed at least 1,000.

The offshore earthquake triggered a tsunami which wreaked havoc on Japan's north-east coast, sweeping far inland and devastating a number of towns and villages.

Japan's Prime Minister Naoto Kan declared a state of emergency at the Fukushima Daiichi and Daini (also known as Fukushima 1 and 2) power plants as engineers try to confirm whether a reactor at one of the stations has gone into meltdown.

The emergency declaration is an automatic procedure after nuclear reactors shut down in the event of an earthquake, allowing officials to take rapid action.
Evacuation zone expanded
Television pictures showed a massive blast at one of the buildings of the Fukushima-Daiichi plant, about 250km (160 miles) north-east of Tokyo.
A huge cloud of smoke billows out and large bits of debris are flung far from the building.
Japan's NHK TV showed before and after pictures of the plant. They appeared to show that the outer structure of one of four buildings at the plant had collapsed after the explosion.
The Tokyo Electric Power Co (Tepco), the plant's operator, said four workers had been injured.
It is not yet clear in exactly what part of the plant the explosion occurred or what caused it.
The government of Fukushima prefecture said radiation levels at the plant over one hour were equivalent to the annual allowable exposure.
Officials ordered the evacuation zone around the plant expanded from a 10km radius to 20km. BBC correspondent Nick Ravenscroft said police stopped him 60km from the Fukushima-Daiichi plant.
Japan's nuclear agency said on Saturday that radioactive caesium and iodine had been detected near the number one reactor of the power station.
The agency said this may indicate that containers of uranium fuel inside the reactor may have begun melting.

Japanese broadcaster NHK screened a before and after image showing the damaged Fukushima plant

The container housing the reactor was not seriously damaged in the explosion, Kyodo news agency quoted the Nuclear and Industrial Safety Agency as saying.
Air and steam, with some level of radioactivity, has been released from several of the reactors at both plants in an effort to relieve the huge amount of pressure building up inside.
Mr Kan said the amount of radiation released was "tiny".
Cooling system failure
Nuclear reactors at four power plants in the earthquake-struck zone automatically shut down on Friday.
In several of the reactors at the two Fukushima plants the cooling systems, which should keep operating on emergency power supplies, failed.
Without cooling, the temperature in the reactor core builds, with the risk that it could melt through its container into the building housing the system.
Pressure also builds in the containers housing the reactor.
Tepco said it was pumping water into the Fukushima-Daiichi's number one reactor in a bid to cool it down.

Analysts say a meltdown would not necessarily lead to a major disaster because light-water reactors would not explode even if they overheated.

But Walt Patterson, of the London research institute Chatham House, said "this is starting to look a lot like Chernobyl".
He said it was too early to tell if the explosion's aftermath would result in the same extreme level of radioactive contamination that occurred at Chernobyl.
The explosion was most likely caused by melting fuel coming into contact with water, he told the BBC.
The 8.9-magnitude tremor struck in the afternoon local time on Friday off the coast of Honshu island at a depth of about 24km, 400km (250 miles) north-east of Tokyo.
It was nearly 8,000 times stronger than last month's quake in New Zealand that devastated the city of Christchurch, scientists said.
Some of the same search and rescue teams from around the world that helped in that disaster are now on their way to Japan.
As relief workers begin to reach the earthquake zone, the scale of the damage is being revealed.
One of the worst-hit areas was the port city of Sendai, in Miyagi prefecture, where police said between 200 and 300 bodies were found in one ward alone.
The town of Rikuzentakada, in Iwate prefecture, was reported as largely destroyed and almost completely submerged. NHK reported that soldiers had found 300-400 bodies there.
Chief government spokesman Yukio Edano said it was believed that more than 1,000 people had died.
A local official in the town of Futuba, in Fukushima prefecture, said more than 90% of the houses in three coastal communities had been washed away by the tsunami.
Looking from the fourth floor of the town hall, I see no houses standing,'' Kyodo news agency quoted him as saying.

Nuclear agency Explosion at Japanese plant

(CNN) -- An explosion sent white smoke rising above a nuclear plant where a massive earthquake and tsunami crippled cooling systems in northeastern Japan, the country's nuclear and industrial safety agency said.

Four workers were injured after the blast at the Fukushima Daiichi plant, the agency said. It was not immediately clear where the blast occurred inside the plant, or what caused it.

One expert said the explosion was "clearly a serious situation," but may not be related to problems inside the plant's nuclear reactor.

Other effects of the tsunami may have caused the blast, said Malcolm Grimston, associate fellow for energy, environment and development at London's Chatham House.

"It's clearly a serious situation, but that in itself does not necessarily mean major (nuclear) contamination," he said.
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Japanese public broadcaster NHK said the injured workers were in the process of cooling a nuclear reactor at the plant by injecting water into its core.

Earlier Saturday Japan's nuclear agency said workers were continuing efforts to cool fuel rods at the plant after a small amount of radioactive material escaped into the air.

The agency said there was a strong possibility that the radioactive cesium monitors detected was caused by the melting of a fuel rod at the plant, adding that engineers were continuing to cool the fuel rods by pumping water around them.

A spokesman for Japan's Nuclear and Industrial Agency earlier said atomic material had seeped out of one of the five nuclear reactors at the Daiichi plant, located about 160 miles (260 kilometers) north of Tokyo.

Authorities evacuated people living 10 kilometers from the reactor after an earthquake and tsunami crippled cooling systems there, as well as at another Tokyo Electric Power Company nuclear plant in Japan's Fukushima prefecture.

"This is a situation that has the potential for a nuclear catastrophe. It's basically a race against time, because what has happened is that plant operators have not been able to cool down the core of at least two reactors," said Robert Alvarez, a senior scholar at the Institute for Policy Studies in Washington.

The evacuations notwithstanding, the nuclear safety agency asserted Saturday that the radiation at the plants did not pose an immediate threat to nearby residents' health, the Kyodo News Agency said.

The International Atomic Energy Agency said Friday on its website that the quake and tsunami knocked out a Daiichi reactor's off-site power source, which is used to cool down the radioactive material inside. Then, the tsunami waves disabled the backup source -- diesel generators -- and authorities were working to get these operating.

On Saturday Japanese nuclear authorities said the cooling system had also failed at three of the four reactors at the Fukushima Daini plant -- located in another town in northeaster Japan's Fukushima prefecture.

Janie Eudy told CNN that her 52-year-old husband, Joe, was working at the Daiichi plant and was injured by falling and shattering glass when the quake struck. As he and others were planning to evacuate, at their managers' orders, the tsunami waves struck and washed buildings from the nearby town past the plant.

"To me, it sounded like hell on earth," she said, adding her husband -- a native of Pineville, Louisiana -- ultimately escaped.

The power company reported Saturday that about 1 million households were without power, and that power shortages may occur due to damage at the company's facility.

"We kindly ask our customers to cooperate with us in reducing usage of power," the company said.

Magnitude Quake hits Japan-Massive 8.9

Tsunami warnings issued for at least 20 countries after quake

Tokyo (CNN) -- An 8.9-magnitude earthquake hit northern Japan on Friday, triggering tsunamis and sending a massive wave filled with debris that included boats and houses inching toward land.

The number of fatalities was unclear, but Japan's Kyodo news reported at least 10 killed and numerous injured.

The quake prompted at least 19 countries and numerous Pacific islands to issue tsunami warnings. It was followed by powerful aftershocks that were felt in capital of Tokyo.

The quake's epicenter was 373 kilometers (231 miles) away from Tokyo, the United States Geological Survey said. But residents there continued to feel aftershocks long after the quake

At Tokyo Station, one of Japan's busiest subway stations, people grabbed each other to steady themselves. Children cried. An announcement over the station loudspeaker warned commuters to remain underground.

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With bus and train lines interrupted, workers and children poured into the streets after offices and schools were closed.

Japanese Prime Minister Naoto Kan appealed for calm and said there were no reported leaks of radioactive materials from power plants.

A spokesman for the U.S. military bases in Japan said there were no immediate reports of significant damage or injuries there.

The quake rattled buildings and toppled cars off bridges and into waters underneath. Waves of debris flowed like lava across farmland, pushing boats, houses and trailers.

Firefighters battled a blaze at an oil refinery in Chiba prefecture near Tokyo.

"This was larger than anyone expected and went on longer than anyone expected," said Matt Alt in Tokyo.

"My wife was the calm one ... she told us to get down and put your back on something, and leave the windows and doors open in case a building shifts so you don't get trapped."

Richard Lloyd Parry said when the quake struck, he looked through a window and saw buildings shaking from side to side.

"Central Tokyo is fine from what we see, people are calm ... and not going inside buildings," he said.

Such a large earthquake at such a shallow depth creates a lot of energy, said Shenza Chen of the U.S. Geological Survey.

It caused a power outage in about 4 million homes in Tokyo and surrounding areas.

A tsunami is sweeping across the Pacific Ocean, with a wall of water heading toward at more than a dozen countries.

An earthquake of that size can generate dangerous tsunamis to coasts outside the source region, the National Weather Service said.

Humanitarian agencies were working with rescue crews to reach the people affected.

"When such an earthquake impacts a developed country like Japan, our concern also turns to countries like the Philippines and Indonesia, which might not have the same resources," said Rachel Wolff, a spokeswoman for World Vision.

Wolff said her agency is helping people on the ground in Japan and teaming up to help others in countries along the path of the tsunami.

In Philippines alone, the tsunami is expected to hit in the early morning and the government has ordered the evacuation of 19 provinces along the coast, which could affect hundreds of thousands of people

Authorities in at least 20 countries and numerous Pacific islands issued tsunami warnings, the National Weather Service said.

The wide-ranging list includes Russia and Indonesia, Central American countries like Guatemala, El Salvador and Costa Rica and the U.S. state of Hawaii, where warning sirens were sounded in the morning.

The tsunami could cause damage "along coastlines of all islands in the state of Hawaii," warned the U.S. National Oceanic and Atmospheric Administration. "Urgent action should be taken to protect lives and property."

Tsunamis are a series of long ocean waves that can last five to 15 minutes and cause extensive flooding in coastal areas. A succession of waves can hit -- often the highest not being the first, said CNN meteorologist Ivan Cabrera.

The quake was the latest in a series in the region this week.

Early Thursday, an earthquake with a preliminary magnitude of 6.3 struck off the coast of Honshu.

A day earlier, a 7.2-magnitude earthquake struck off of Honshu, the country's meteorological agency said.

The largest recorded quake took place in Chile on May 22, 1960, with a magnitude of 9.5, the USGS said. Thursday's quake was the fifth-strongest in the world since 1900, the agency said.