A second explosion has rocked a nuclear power plant in Japan. The plant is in an area that was devastated by a massive earthquake and tsunami on Friday.
The explosion occurred mid-morning Monday, while workers were battling to bring down temperatures inside the Fukushima Number One nuclear power plant's number three reactor.
Television images showed a strong explosion obliterating the upper walls of the reactor building and causing a huge plume of white smoke.
Chief Cabinet Secretary Yukio Edano spoke moments later at a news conference, saying the explosion appears similar to one that occurred Saturday at the same plant's number one reactor.
That was sparked with hydrogen, which was being vented to relieve pressure, mixed with oxygen.
Officials at the plant say Saturday's explosion destroyed the operations floor of the reactor building, but did not damage the reactor's containment vessel or core.
Pressure and temperature levels at the reactor had been very high since a large tsunami on Friday disabled generators running its cooling system.
Earlier Monday, workers had been evacuated because of dangerously high pressure levels.
Tokyo Electric Power company, which operates the plant, said an undetermined number of workers had been injured in the blast.
The government advised anyone within 20 kilometers of the power station to stay indoors and close windows. Several people were exposed to radiation following Saturday's blast.