There has been a second explosion at the Fukushima nuclear plant in northern Japan that was damaged in Friday’s earthquake and tsunami. Eleven people were hurt in the blast, which sent a plume of smoke into the air.
The fuel rods at the reactor are now partly exposed, raising fears of a meltdown.
Officials said the core of the reactor is intact and the risk of a large-scale radiation leak is low.
Shortly after the explosion it was reported that the cooling system had failed on a third reactor at the plant. This sequence of events is what preceded the blasts at other reactors.
The authorities are playing down any risk to health, but the US has moved one of its aircraft carriers 160 kilometres offshore after low-level radiation was detected.
Tens of thousands of people have been evacuated from the area. Some 22 people are reportedly being treated for radiation exposure.