Another fire broke out on Wednesday at an earthquake-crippled Japanese nuclear plant that has sent low levels of radiation wafting into Tokyo and triggered international alarm, suggesting that the crisis may be slipping out of control.
Academics and nuclear experts agree that the solutions being proposed to contain damage to the Daiichi reactors at Fukushima, 240 km (150 miles) north of Tokyo, are last-ditch efforts to stem what could well be remembered as one of the world's worst industrial disasters.
While public broadcaster NHK said flames were no longer visible at the building housing the No.4 reactor of the plant, Japanese TV pictures showed smoke rising from the facility at mid-morning (1000 local, 0100 GMT).
Experts say spent fuel rods in a cooling pool at the No. 4 reactor could be exposed by the fire and spew more radiation into the atmosphere. Operator Tokyo Electric Power said it was considering using a helicopter to dump boric acid, a fire retardant, on the facility.
Japan's Nuclear and Industrial Safety Agency said two workers were missing after blasts at the facility a day earlier blew a hole in the building housing the No. 4 reactor.
In the first hint of international frustration at the pace of updates from Japan, Yukiya Amano, director general of the International Atomic Energy Agency, said he wanted more timely and detailed information.
"We do not have all the details of the information so what we can do is limited," Amano told a news conference in Vienna. "I am trying to further improve the communication."
Several experts said that Japanese authorities were underplaying the severity of the incident, particular on a scale called INES used to rank nuclear incidents. The Japanese have so far rated the accident a four on a one-to-seven scale, but that rating was issued on Saturday and since then the situation has worsened dramatically.
"This is a slow-moving nightmare," said Dr Thomas Neff, a research affiliate at the Center for International Studies, which is part of the Massachusetts Institute of Technology. "This could be a five or a six -- it's premature to say since this event is not over yet."
France's nuclear safety authority ASN said Tuesday it should be classed as a level-six incident.
Japanese Prime Minister Naoto Kan on Tuesday urged people within 30 km (18 miles) of the facility -- a population of 140,000 -- to remain indoors, as authorities grappled with the world's most serious nuclear accident since the Chernobyl disaster in Ukraine in 1986.
Officials in Tokyo said radiation in the capital was 10 times normal at one point but not a threat to human health in the sprawling high-tech city of 13 million people.
The best advice experts could give them was to stay indoors, close the windows and avoid breathing bad air -- steps very similar to those for handling a smog alert or avoiding influenza.
While these steps may sound inconsequential, experts said the danger in Tokyo, while worrisome, is slight -- at least for now.
"Everything I've seen so far suggests there have been nominal amounts of material released. Therefore, the risks are generally low to the population," Jerrold Bushberg, who directs programs in health physics at the University of California at Davis, said in a telephone interview.
Winds over the plant will blow from the north along the Pacific coast early on Wednesday and then from the northwest towards the ocean during the day, the Japan Meteorological Agency said.
Fears of trans-Pacific nuclear fallout sent consumers scrambling for radiation antidotes in the U.S. Pacific Northwest and Canada. Authorities warned people would expose themselves to other medical problems by needlessly taking potassium iodide in the hope of protection from cancer.
The nuclear crisis and concerns about the economic impact from last week's earthquake and tsunami have hammered Japan's stock market.
The Nikkei index was up over 5 pct in early trading on Wednesday after ending down 10.6 percent on Tuesday and 6.2 percent the day before. The fall wiped some $620 billion off the market.
SCRAMBLE TO STOP WATER EVAPORATING
Authorities have spent days desperately trying to prevent the water which is designed to cool the radioactive cores of the reactors from evaporating, which would lead to overheating and the release of dangerous radioactive material into the atmosphere.
"The possibility of further radioactive leakage is heightening," a grim-faced Kan said in his address to the nation on Tuesday.
"We are making every effort to prevent the leak from spreading. I know that people are very worried but I would like to ask you to act calmly."
Levels of 400 millisieverts per hour had been recorded near the No. 4 reactor, the government said. Exposure to over 100 millisieverts a year is a level which can lead to cancer, according to the World Nuclear Association.
The plant operator, Tokyo Electric Power Co. , pulled out 750 workers, leaving just 50, and a 30-km (19 mile) no-fly zone was imposed around the reactors. There have been no detailed updates on what levels the radiation reached inside the exclusion zone.
Despite pleas for calm, residents rushed to shops in Tokyo to stock up on supplies. Don Quixote, a multi-storey, 24-hour general store in Roppongi district, sold out of radios, flashlights, candles and sleeping bags.
Several embassies advised staff and citizens to leave affected areas in Japan. Tourists cut short vacations and multinational companies either urged staff to leave or said they were considering plans to move outside Tokyo.
German technology companies SAP and Infineon were among those moving staff to safety in the south. SAP said it was evacuating its offices in Tokyo, Osaka and Nagoya and had offered its 1,100 employees and their family members transport to the south, where the company has rented a hotel for
"Everyone is going out of the country today," said Gunta Brunner, a 25-year-old creative director from Argentina preparing to board a flight at Narita airport. "With the radiation, it's like you cannot escape and you can't see it."
"WHAT THE HELL IS GOING ON?"
Japanese media have became more critical of Kan's handling of the disaster and criticised the government and the nuclear plant operator for their failure to provide enough information on the incident.
Kan himself lambasted the operator for taking so long to inform his office about one of the blasts on Tuesday, Kyodo news agency reported.
Kyodo said Kan had ordered TEPCO not to pull employees out of the plant. "The TV reported an explosion. But nothing was said to the premier's office for about an hour," a Kyodo reporter quo