11 injured in nuclear plant blast
The second hydrogen blast in three days has rocked Japan's earthquake-stricken Fukushima Dai-ichi nuclear power plant, sending a massive column of smoke into the air and injuring 11 people.
Chief Cabinet Secretary Yukio Edano said four army personnel and seven nuclear power plant workers were hurt when Unit 3 exploded.
Mr Edano said one of the workers was seriously injured but still conscious and the four military staff were only slightly hurt and had already returned to their unit.
Later in the day, another reactor at the plant lost its cooling capacity, raising the risk of another explosion.
The US said it had shifted its offshore forces away from the plant after detecting low-level radioactive contamination.
The aircraft carrier USS Ronald Reagan was about 100 miles offshore when it detected the radiation, which US officials said was about the same as one month's normal exposure to natural background radiation.
It was not clear if the radiation had leaked during today's explosion. The blast was felt 25 miles away, but the plant's operator said radiation levels at the reactor were still within legal limits.
The explosion at the plant's Unit 3, which authorities have been frantically trying to cool after a system failure in the wake of Friday's massive earthquake and tsunami, triggered an order for hundreds of people to stay indoors, said Mr Edano. The two disasters left at least 10,000 people dead.
Operators knew an explosion was a possibility as they struggled to reduce pressure inside the reactor containment vessel, but apparently felt they had no choice if they wanted to avoid a complete meltdown. In the end, the hydrogen in the released steam mixed with oxygen in the atmosphere and set off the blast.
Tokyo Electric Power Co, which operates the plant, said radiation levels at Unit 3 were well under the levels where a nuclear operator must file a report to the government. On Saturday, a similar explosion took place at the plant's Unit 1, injuring four workers and causing mass evacuations.