A meltdown may be under way at one of Fukushima Daiichi's nuclear power reactors, an official with Japan's nuclear and industrial safety agency told CNN Sunday.
A meltdown is a catastrophic failure of the reactor core, with a potential for widespread radiation release. However, Toshiro Bannai, director of the agency's international affairs office, expressed confidence that efforts to control the crisis would prove successful.
Meanwhile, a second reactor at the same facility failed shortly after 5 a.m. Sunday, the Tokyo Electric Power Company said, according to TV Asahi. The power company said it was having difficulty cooling the reactor and may need to release radioactive steam in order to relieve pressure.