SOMA, Japan (AP) - A fire broke out at a nuclear reactor again Wednesday, a day after the power plant emitted a burst of radiation that panicked an already edgy Japan and left the government struggling to contain a spiraling crisis caused by last week's earthquake and tsunami.
The outer housing of the containment vessel at the No. 4 unit at the Fukushima Dai-ichi nuclear complex erupted in flames early Wednesday, said Hajimi Motujuku, a spokesman for the plant's operator, Tokyo Electric Power Co.
On Tuesday, a fire broke out in the reactor's fuel storage pond - an area where used nuclear fuel is kept cool - causing radioactivity to be released into the atmosphere. Tokyo Electric Power said the new blaze erupted early Wednesday because the initial fire had not been fully extinguished. Firefighters were trying to put out the latest blaze.
About three hours after the blaze erupted Wednesday, Japan's nuclear safety agency said fire and smoke could no longer be seen at Unit 4, but that it was unable to confirm that the blaze had been put out.
Also Wednesday, Japan's nuclear safety agency said 70 percent of the nuclear fuel rods may have been damaged at another Fukushima Dai-ichi reactor that was first stricken last week, triggering the crisis.
"But we don't know the nature of the damage, and it could be either melting, or there might be some holes in them," said an agency spokesman, Minoru Ohgoda.
Japan's national news agency, Kyodo, said 33 percent of the fuel rods at a second reactor were also damaged.
Radiation levels in areas around the nuclear plant rose early Tuesday afternoon but appeared to subside by evening, officials said. But the unease remained in a country trying to recover from the massive disasters that are believed to have killed more than 10,000 people and battered the world's third-largest economy.
The radiation leak caused the government to order 140,000 people living within 20 miles of the plant to seal themselves indoors to avoid exposure, and authorities declared a ban on commercial air traffic through the area. Worries about radiation rippled through Tokyo and other areas far beyond that cordon. The stock market plunged for a second day, dropping 10 percent.
The troubles cascaded Tuesday at the Dai-ichi plant, where there have already been explosions at two reactor buildings since Friday's disasters. An explosion at a third reactor blasted a 26-foot hole in the building and, experts said, damaged a vessel below the reactor, although not the reactor core. Three hours later, a fire broke out at a fourth reactor, which had been offline for maintenance.
In a nationally televised address Tuesday, Prime Minister Naoto Kan said radiation had seeped from four of the plant's six reactors. The International Atomic Energy Agency said Japanese officials informed it that the fire was in a pool where used nuclear fuel rods are stored and that "radioactivity is being released directly into the atmosphere." Long after the fire was extinguished, a Japanese official said the pool might still be boiling.
Depending on how bad the blast was at Unit 2, experts said more radioactive materials could seep out. If the water in the storage pond in Unit 4 boils away, the fuel rods could be exposed, leaking more virulent radiation.
Experts noted that much of the leaking radiation was apparently in steam from boiling water - and the falling radiation levels suggest the situation could be stabilizing.
Government spokesman Yukio Edano said the radiation leak potentially affected public health. But authorities and experts said the risks to the public diminished the farther the distance from the plant. At its most intense, the leak released a radioactive dose in one hour at the site 400 times the amount a person normally receives in a year. Within six hours, that level had dropped dramatically.
A person would have to be exposed to that dose for 10 hours for it to be fatal, said Jae Moo-sung, a nuclear engineering expert at Seoul's Hanyang University.
Radiation elsewhere never reached that level. In Tokyo, 170 miles to the southwest, authorities reported radiation levels nine times normal - too small, officials said, to threaten the 39 million people in and around the capital. Weather patterns helped, shifting Tuesday night to the southeast, blowing any potential radiation from the plant toward the sea.
"It's not good, but I don't think it's a disaster," said Steve Crossley, an Australia-based radiation physicist. "If the radioactive material gets out, it's a major problem. That doesn't appear to be happening in Japan, and that's the big difference. As long as you are not near it, it doesn't pose a health risk."
The IAEA said Tuesday that all other Japanese nuclear plants were in a safe and stable condition.
Though Kan and other officials urged calm, the 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.
In evacuation centers for people living near the plant, Japanese worried about radiation contamination, calling it an unseen threat, and complained that the government was not forthcoming with information.
"Nuclear power is the most frightening, even more than a tsunami. The government, the ruling party, administrators, nobody tells us, the citizens, what is really happening," Isao Araki, 63, said at an evacuation center.
Kan's government has been more open and transparent than previous administrations in keeping the nation informed of developments in the nuclear crisis. Edano, his top spokesman, appears frequently before the press with updates that have been widely praised for their frankness and clarity.
Quake, tsunami aftermath
The radiation fears added to the catastrophe that has been unfolding in Japan. Four days after the 9.0-magnitude earthquake and tsunami, millions of people strung out along the east coast had little food, water or heat, and already chilly temperatures dropped further as a cold front moved in. Up to 450,000 people are in temporary shelters
Officials have only confirmed about 3,300 deaths, but officials have said the toll was likely to top 10,000 in one of the four hardest-hit areas. Experts involved in the 2004 Asian tsunami said there was no question more people died, despite Japan's high state of preparation, and like the earlier disaster, many thousands may never be found.
In a rare bit of good news, rescuers found two survivors Tuesday, one of them a 70-year-old woman whose house was torn off its foundation by the tsunami.
Mostly, though, search teams found few signs of life. More than 200 rescue crews from the U.S. and Britain poured Tuesday into the coastal city of Ofunato, finding little but rubble and people looking for lost possessions. Whole city blocks lay flattened. A yacht came to rest atop the remains of a two-story gas station.
Meanwhile, Japan has been rattled by a couple of aftershocks within minutes, causing buildings in Tokyo to sway.
The first, measuring 6.2 in magnitude, struck Tuesday night off the coast of Fukushima prefecture, 200 miles northeast of Tokyo and near where a massive quake hit last week.
Three minutes later, a second 6.0-magnitude quake rumbled under Shizuoka prefecture, 55 miles southwest of Tokyo.