Second explosion at Japan nuclear reactor

A second explosion has hit the nuclear plant in Japan that was damaged in Friday's earthquake – but officials said it had resisted the blast.

Japan's nuclear safety agency said the explosion was believed to have been caused by the build-up of hydrogen.

Experts said the reactor core was still intact, and that radiation levels were below legal limits.

Technicians have been battling to cool three reactors at the Fukushima Daiichi plant since Friday, when the quake and tsunami ruined the the cooling system.

The government said an operation pumping seawater into the reactors to help lower the temperature was still going on despite the explosion.