A possible breach at Japan's troubled nuclear plant escalated the crisis anew Friday, two weeks after an earthquake and tsunami first compromised the facility.
The development suggested radioactive contamination may be worse than first thought, with tainted groundwater the most likely consequence.
Japanese leaders defended their decision not to evacuate people from a wider area around the Fukushima Dai-ichi plant in northeastern Japan, insisting they are safe if they stay indoors. But officials also said residents may want to voluntarily move to areas with better facilities, since supplies in the tsunami-devastated region are running short.
The escalation in the nuclear plant crisis came as the death toll from the quake and tsunami passed 10,000 on Friday. Across the battered northeast coast, hundreds of thousands of people whose homes were destroyed still have no power, no hot meals and, in many cases, no showers for 14 days.
The uncertain nuclear situation again halted work at the Fukushima complex, where authorities have been scrambling to stop the overheated facility from leaking dangerous radiation. Low levels of radiation have been seeping out since the March 11 quake and tsunami knocked out the plant's cooling system, but a breach could mean a much larger release of contaminants, threatening the groundwater.
"The situation today at the Fukushima Dai-ichi power plant is still very grave and serious. We must remain vigilant," Prime Minister Naoto Kan said. "We are not in a position where we can be optimistic. We must treat every development with the utmost care."
The possible breach in the plant's Unit 3 might be a crack or a hole in the stainless steel chamber of the reactor core or in the spent fuel pool that is lined with several feet of reinforced concrete. The temperature and pressure inside the core, which holds the fuel rods, remained stable and was far lower than what would further melt the core.
Suspicions of a possible breach were raised when two workers suffered skin burns after wading into water 10,000 times more radioactive than levels normally found in water in or around a reactor, the Nuclear and Industrial Safety Agency said.
Water with equally high radiation levels was found in the Unit 1 reactor building, according to Tokyo Electric Power Co., which operates the plant. Water was also discovered in Units 2 and 4, and the company said it suspects that, too, is radioactive. Officials acknowledged the water would delay work inside the plant.
Plant officials and government regulators say they don't know the source of the radioactive water discovered at Units 1 and 3. It could have come from a leaking reactor core, associated pipes or a spent fuel pool. Or it may be the result of overfilling the pools with emergency cooling water.
Friday marked two weeks to the day since the magnitude-9.0 quake triggered a tsunami that flattened cities along the northeastern coast. With the cleanup and recovery operations continuing and more than 17,400 listed as missing, the final number of dead was expected to surpass 18,000.
Kan apologized to farmers and business owners for the toll the radiation has had on their livelihoods: Several countries have halted some food imports from areas near the plant after elevated levels of radiation were found in raw milk, sea water and 11 kinds of vegetables, including broccoli, cauliflower and turnips.
He also thanked utility workers, firefighters and military personnel for "risking their lives" to cool the facility.
Officials have evacuated residents within 12 miles of the nuclear plant and advised those up to 20 miles away to stay indoors to minimize exposure. The U.S. has recommended that people stay 50 miles away from the plant.
Government spokesman Yukio Edano insisted that people living 12 to 20 miles from the plant should still be safe from radiation as long as they stay indoors. But since supplies are not being delivered to the area fast enough, he said it may be better for residents to voluntarily evacuate.
"If the current situation is protracted and worsens, then we will not deny the possibility of (mandatory) evacuation," he said.
Edano said the government "will continue to revisit this and as we have done so, we will provide whatever advice as necessary. Safety is the priority."
NISA spokesman Hidehiko Nishiyama said later that Tokyo Electric was issued a "very strong warning" for safety violations and that a thorough review would be conducted once the situation stabilizes.