A second explosion has hit a Japanese nuclear plant that was damaged in Friday's earthquake, but officials said the reactor core was still intact.
A huge column of smoke billowed from Fukushima Daiichi's reactor 3, two days after a blast hit reactor 1.
The latest explosion, said to have been caused by a hydrogen build-up, injured 11 people, one of them seriously.
Soon afterwards, the government said a third reactor at the plant had lost its cooling system.
Water levels were now falling at reactor 2, which is to be doused with sea water, said government spokesman Yukio Edano.
A similar cooling system breakdown preceded the explosions at reactors 1 and 3.
