Emergency officials ordered the evacuation Saturday of all civilians within a six-mile radius of the Fukushima No. 1 plant, which is about 150 miles northeast of Tokyo, after its normal backup cooling systems failed and it became necessary to release radioactive steam to relieve pressure that could cause an explosion.
Several hours later, authorities revealed that cooling systems at the Fukushima No. 2 plant, a few miles south, had also failed, and evacuations were ordered around that plant as well. In all, five reactors at the two plants were damaged.