Explosion heard at Japan's Fukushima nuclear plant

News agency quotes says smoke also seen at Tokyo plant; authorities fear possible meltdown but say risk of radiation contamination small.

Kashiwazaki-Kariwa nuclear power plant (R) 311 (photo credit: REUTERS/Issei Kato)
Kashiwazaki-Kariwa nuclear power plant (R) 311
(photo credit: REUTERS/Issei Kato)
TOKYO - An explosion was heard and smoke was seen at Tokyo Electric Power Co 's Fukushima nuclear power plant, Jiji news agency quoted the police as saying on Saturday.
Japan earlier in the day warned of a meltdown at the nuclear reactor damaged when a massive earthquake and tsunami struck the northeast coast, but said the risk of radiation contamination was small.
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Pressure was building in reactors of two plants at Tokyo Electric Power Co 's Fukushima facility, located some 240 km (150 miles) north of Tokyo. At one of them, the Daiichi plant, pressure was set to released soon , which could result in a radiation leak, officials said.
"It's possible that radioactive material in the reactor vessel could leak outside but the amount is expected to be small, and the wind blowing towards the sea will be considered," Chief Cabinet Secretary Yukio Edano told a news conference.
"Residents are safe after those within a 3 km radius were evacuated and those within a 10 km radius are staying indoors, so we want people to be calm," he added.
A trade ministry official said that TEPCO was also considering releasing pressure at its other plant, the Daini plant.
TEPCO said it had lost ability to control pressure in some of the reactors at the Daini plant as it had with the Daiichi plant. Pressure wa s stable inside the reactors of the Daini plant but rising in the containment vessels, a spokesman said.
Some 3,000 people who live within a 3 km radius of the plant had been evacuated, Kyodo news agency said.
Pressure at one Daiichi reactor may have risen to 2.1 times the designed capacity, the trade ministry said. Media also said the radiation level was rising in the turbine building.
Preparatory work for the releasing of the pressure was expected to take time , Kyodo reported. R adiation levels outside the main gate of the plant were eight times normal levels.