The death toll in Japan's earthquake and tsunami could exceed 10,000 in one northeastern state alone, an official said Sunday, as National Broadcaster NHK reported that one nuclear plant suffered a partial meltdown.
Meanwhile millions of survivors of the quake were left without drinking water, electricity or proper food — as aftershocks continued.
"This is Japan's most severe crisis since the war ended 65 years ago," Prime Minister Naoto Kan told reporters, adding that Japan's future would be decided by the response to this crisis.
The police chief of Miyagi prefecture, or state, told a gathering of disaster relief officials that his estimate for deaths was more than 10,000, police spokesman Go Sugawara said. Miyagi has a population of 2.3 million and is one of the three prefectures hardest hit in Friday's disaster. Only 379 people have officially been confirmed dead in Miyagi.
Meanwhile, the nation continued attempts to avert possible disaster as nuclear cores at two Japanese power plants overheated.
The threat prompted the evacuation of more than 200,000 people living within 12 miles of the Fukushima No. 1 plant, also known as Daishi, one of six reactors at the site 170 miles northeast of Tokyo.
Reports said that some radioactive iodine and cesium were released from the plant after an explosion blew the roof off a building housing a reactor.
At Fukushima No. 1, engineers are flooding reactor unit No. 1 with sea-water after its cooling system failed. Some fuel rods may have been damaged and partially melted. Another reactor at this complex is having cooling trouble as well. The lack of electrical power has kept water pumps from circulating enough water through the reactor core.
Engineers have had to vent radioactive vapor to relieve high pressure and avoid an explosion like the one that struck the complex on Saturday. It damaging the exterior walls of the building where the reactor is placed, but not the actual metal housing enveloping the reactor.
The government said radiation emanating from the plant appeared to have decreased after the blast, which produced an intensifying cloud of white smoke that swallowed the complex.
"Radiation so far is onsite and it's not at acute lethal levels, but it is of great concern," NPR's Christopher Joyce reported.
Officials also relieved excess pressure in the containment that houses a second reactor in the same nuclear complex. Pressure from steam can rise to dangerous levels and even destroy the containment building, which is designed to keep radioactive gases from escaping into the atmosphere in an accident, Joyce reported.
About 7 miles to the south, at Fukushima No. 2 — also known as Daini — nuclear complex, there are four more reactors. The International Atomic Energy Agency reports that these plants do have electricity for cooling.
In towns near the reactors, residents are lining up to be tested for radiation exposure. NPR's Doualy Xaykaothao visited a testing facility in Koriyama City, where 1,500 people have been seen so far. But, she says, "Its not yet clear who's been exposed, and how dangerous the level."
Japan dealt with the nuclear threat as it was suffering from Friday's double disaster that pulverized the northeastern coast, leaving at least 686 people dead by official count.
The full scale of destruction was not yet known, but there were grim signs that the death toll could soar. The country has been rattled by more than 150 aftershocks since the initial quake, including a strong one off its eastern coast, closer to Tokyo.
Trying To Cool The Reactor
The extent of the ongoing danger from the explosion at the nuclear plant in Fukushima is unclear. Authorities pumped seawater mixed with boron into the damaged nuclear reactor, a strategy nuclear engineering experts in the U.S. say may never have been tried before, Joyce reported. He said one expert called it a "hail Mary" effort.
Boron helps dampen the nuclear reaction that produces heat in the reactor, Joyce said. Seawater has the advantage of being plentiful at the coastal power plant, but it will eventually corrode and ruin the metal structures in the cooling system.
The reactor lost power following the earthquake and tsunami. Electricity is necessary to run the water through the reactor vessel and cool the uranium fuel rods, Joyce said. Japanese engineers have been struggling for two days to get the freshwater cooling system back up to keep the hot reactor core from melting.
Chief Cabinet Secretary Yukio Edano said efforts to add cooling water to the reactor core had resulted in the production of hydrogen gas, which built up inside the building and then exploded, injuring four workers.
Evacuations Expand Around Power Plant
NPR's Doualy Xaykaothao reported that aftershocks continued to rattle the northeast part of the country.
"I've felt at least three and they were quite strong," she reported from Fukushima. "There were times where many of us had to step out of the building, fearing that there would be some kind of collapse."
She said local media warned there would be more tsunamis.
Evacuation in the city widened throughout the day, expanding from a 3-mile radius to 12 miles or more around the power plant. People in the expanded area were advised to leave quickly; 51,000 residents were previously evacuated.
Officials have not given specific radiation readings for the area, though they said they were elevated before the blast. At one point, the plant was releasing each hour the amount of radiation a person normally absorbs from the environment each year.
"The government continues to say that [the level of radiation in the area] is still not harmful," Xaykaothao said. According to official sources, it's not to a point where people should be alarmed.
Authorities were planning to distribute iodine to residents in the area, according to the International Atomic Energy Agency. Iodine counteracts the effects of radiation.
But, Xaykaothao said, "the community here is certainly not taking any chance; a lot of people are staying away — it's almost a ghost town on some of these streets."
"Everyone wants to get out of the town. But the roads are terrible," said Reiko Takagi, a middle-aged woman, standing outside a taxi company. "It is too dangerous to go anywhere. But we are afraid that winds may change and bring radiation toward us."
The Transport Ministry said all highways from Tokyo leading to quake-hit areas were closed, except for emergency vehicles. Mobile communications were spotty and calls to the devastated areas were going unanswered.
Emergency Work Continues In Wake Of Tsunami
The concerns about a radiation leak at the nuclear power plant overshadowed the massive tragedy laid out along a 1,300-mile stretch of the coastline where scores of villages, towns and cities were battered by the tsunami, packing 23-feet high waves.
It swept inland about six miles in some areas, swallowing boats, homes, cars, trees and everything else.
Images from Japan show scenes of devastation: flooded cities and highways and twisted piles of wreckage where homes once stood. Cars and trucks are strewn haphazardly where the force of the water left them. Hundreds of people were killed, many more are homeless and thousands are without power and water.
"In some areas, the tsunami reached up to six miles inland," NPR's Rob Gifford reported. The tsunami itself was about 30 feet high; 200,000 people are said to have fled.
"There are towns that have been completely flattened," he said. "I'm not sure they're going to find any survivors."
According to official figures, 642 people were missing and 1,426 injured. In addition, police said between 200 and 300 bodies were found along the coast in Sendai, the biggest city in the area near the quake's epicenter.
Local TV stations broadcast footage of people lining up for water and food such as rice balls. In Fukushima, city officials were handing out bottled drinks, snacks and blankets. But there were large areas that were surrounded by water and were unreachable.
Rescuers En Route
Meanwhile, the first wave of military rescuers began arriving by boats and helicopters.
Prime Minister Naoto Kan said 50,000 troops joined rescue and recovery efforts, aided by boats and helicopters.
"The Japanese government has mobilized very quickly," Gifford reported, sending several hundred planes to airports in the north of the main island. "Military and civilian groups have all been moving into the area to try to help the people whose homes have literally vanished. And there are tens of thousands of those people."
Dozens of countries also offered help. President Obama pledged U.S. assistance following what he called a potentially "catastrophic" disaster. Washington has also dispatched urban search and rescue teams, according to U.S. Ambassador John Roos.
Technologically advanced Japan is well prepared for quakes and its buildings can withstand strong jolts, even a temblor like Friday's, which was the strongest the country has experienced since official records started in the late 1800s. What was beyond human control was the killer tsunami that followed.
Japan's worst previous quake was a magnitude 8.3 temblor in Kanto that killed 143,000 people in 1923, according to the USGS. A magnitude 7.2 quake in Kobe killed 6,400 people in 1995.
Japan lies on the "Ring of Fire" — an arc of earthquake and volcanic zones stretching around the Pacific where about 90 percent of the world's quakes occur, including the one that triggered the Dec. 26, 2004, Indian Ocean tsunami that killed an estimated 230,000 people in 12 countries. A magnitude-8.8 quake that shook central Chile in February 2010 also generated a tsunami and killed 524 people.
NPR's Christopher Joyce, Jon Hamilton, Rob Gifford and freelance journalist Doualy Xaykaothao contributed to this report, which contains material from The Associated Press. Copyright 2011 National Public Radio.