Japan has declared a nuclear power emergency situation following Friday's devastating earthquake, although there have been no reports of radiation leaks at any of the country's nuclear facilities.
The chief cabinet secretary, Yukio Edano, said the nuclear power plant in Fukushima developed a mechanical failure in the reactor cooling system after it was shut down during the earthquake, reports the UK's Guardian. He said the measure was a precaution and there was no radiation leak at the Fukushima No. 1 power plant. He said the facility was not in immediate danger.
"Parts of nuclear plants were automatically shut down but we haven't confirmed any effects induced by radioactive materials outside the facilities," Prime Minister Naoto Kan said.
Separately, a fire broke out at Tohoku Electric Power's (Tepco) Onagawa nuclear plant in north-eastern Japan after the region was rocked by a series of powerful earthquakes and several tsunamis, some reportedly as high as 10 metres.
The blaze was in a building housing the turbine at the Onagawa plant in Miyagi prefecture. Smoke was observed coming out of the building, which is separate from the plant's reactor.
Eleven nuclear reactors were automatically shut down in the quake-affected area, the industry ministry said.
The four nuclear power plants closest to the epicentre of Friday's earthquake had all been safely shut down, the International Atomic Energy Agency (IAEA) said, adding that it was seeking more information.
The danger is not over, however. Officials have warned of further strong aftershocks and tsunamis. "The four Japanese nuclear power plants closest to the quake have been safely shut down," the IAEA said in a statement. "The agency has sent an offer of good offices to Japan, should the country request support."