Japan's nuclear safety agency says the evacuation order to more than 2,800 people followed the government's declaration at a nuclear power plant after its cooling system failed following a massive earthquake Friday.
The agency says plant workers are currently scrambling to restore cooling water supply at the Fukushima No. 1 power plant.
There was no prospect for an immediate success.
The plant experienced a mechanical failure in the backup power generation system to supply water needed to cool the reactor.
The reactor core remains hot even after a shutdown.
Chief Cabinet Secretary Yukio Edano said that the plant was not in immediate danger of radiation leak.
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