The world's worst nuclear crisis since Chernobyl rose to a new level Wednesday as another fire erupted at Japan's stricken nuclear complex and engineers worried about the possibility of blasts at two other reactors. In addition, two workers were reported missing after an earlier fire.
The new fire broke out Wednesday morning at Unit 4 of the Fukushima Dai-ichi plant. A blast and fire at Unit 4 nearly 24 hours earlier opened a hole in the outer building, emitting radiation from overheating spent fuel in a storage pool.
Two workers inside the unit were missing after the first fire, Japan's nuclear safety agency said.
Officials were also concerned about Units 5 and 6.
"Plant operators were considering the removal of panels from units 5 and 6 reactor buildings to prevent a possible buildup of hydrogen," the International Atomic Energy Agency said in a statement.
"It was a buildup of hydrogen at units 1, 2, and 3 that led to explosions at the Dai-ichi facilities in recent days," it added.
Units 5 and 6 were loaded with nuclear fuel but not producing when Friday's quake and tsunami struck. They had been considered stable, but on Tuesday a senior Japanese official said temperatures there were also slightly elevated.
"The power for cooling is not working well and the temperature is gradually rising, so it is necessary to control it," Chief Cabinet Secretary Yukio Edano told reporters.
Japanese officials told the IAEA that the spent fuel storage area had caught fire and that radioactivity was "being released directly into the atmosphere."