SOMA, Japan — Dangerous levels of radiation leaking from a crippled nuclear plant forced Japan to order 140,000 people to seal themselves indoors Tuesday after an explosion and a fire dramatically escalated the crisis spawned by a deadly tsunami.
In a nationally televised statement, Prime Minister Naoto Kan said radiation has spread from the four stricken reactors of the Fukushima Dai-ichi nuclear plant along Japan's northeastern coast. The region was shattered by Friday's 9.0-magnitude earthquake and the ensuing tsunami that is believed to have killed more than 10,000 people, plunged millions into misery and pummeled the world's third-largest economy.
Japanese officials told the International Atomic Energy Agency that the reactor fire was in a storage pond and that "radioactivity is being released directly into the atmosphere." Long after the fire was extinguished, a Japanese official said the pool, where used nuclear fuel is kept cool, might be boiling.
"We cannot deny the possibility of water boiling" in the pool, said Hidehiko Nishiyama, an official with the economy ministry, which oversees nuclear safety.
That reactor, Unit 4, had been shut down before the quake for maintenance.
If the water boils, it could evaporate, exposing the rods. The fuel rods are encased in safety containers meant to prevent them from resuming nuclear reactions, nuclear officials said, downplaying the risk of that happening.
But they acknowledged that there could have been damage to the containers. They also confirmed that the walls of the storage pool building were damaged.
Though Kan and other officials urged calm, Tuesday's developments fueled a growing panic in Japan and around the world amid widespread uncertainty over what would happen next. In the worst case scenario, one or more of the reactor cores would completely melt down, a disaster that could spew large amounts of radioactivity into the atmosphere.