An explosion that sent white smoke rising above the Fukushima Daiichi plant Saturday afternoon buckled the walls of a concrete building that surrounded one of the plant's nuclear reactors, but did not damage the reactor itself, Chief Cabinet Secretary Yukio Edano told reporters.
The explosion was caused, he said, by a failure in a pumping system as workers tried to prevent the reactor's temperature from racing out of control.
While Edano said radiation levels appeared to be falling after the explosion, the government nevertheless ordered an expanded evacuation of the area around the Daiichi plant, as well as a second facility where the cooling system had failed -- the Fukushima Daini plant.
