TOKYO » A possible breach at Japan’s troubled nuclear plant has escalated the crisis anew, two full 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 plant, insisting they are safe if they stay indoors. But officials 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. 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 two weeks.

The uncertain nuclear situation delayed efforts to stop the overheated Fukushima Dai-ichi nuclear plant from leaking dangerous radiation.

Work was under way Saturday to inject fresh water into one unit, said Hidehiko Nishiyama, a spokesman for Japan’s Nuclear and Industrial Safety Agency, or NISA, amid concerns about dumping large amounts of potentially corrosive seawater onto the reactors.

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. The most likely consequence would be contamination of the groundwater.

"The situation today at the Fukushima Dai-ichi power plant is still very grave and serious. We must remain vigilant," a somber Prime Minister Naoto Kan said Friday night. "We are not in a position where we can be optimistic. We must treat every development with the utmost care."

Water with equally high radiation levels was found in the Unit 1 reactor building, Tokyo Electric Power Co. officials said. 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.

Radioactivity in seawater just outside one unit tested some 1,250 times higher than normal, probably from both airborne radiation released from the reactors and contaminated water leaked into the sea, Nishiyama said Saturday.

But he said the amount posed no immediate health risk.

Plant officials and government regulators say they don’t know the source of the radioactive water discovered at units 1 and 3 of the six-unit complex. 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.

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’s 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, NISA said.

The prime minister 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.

Elevated levels of radiation have turned up elsewhere, including the tap water in several areas of Japan. In Tokyo, tap water showed radiation levels two times higher than the government standard for infants, who are particularly vulnerable to cancer-causing radioactive iodine, officials said.

The scare caused a run on bottled water in the capital, and Tokyo municipal officials are distributing it to families with babies.

The nuclear crisis has compounded the challenges faced by a nation already saddled with a humanitarian disaster. Much of the frigid northeast remains a scene of despair and devastation, with Japan struggling to feed and house hundreds of thousands of homeless survivors, clear away debris and bury the dead.

"It’s still like I’m in a dream," said Tomohiko Abe, a 45-year-old machinist who was in the devastated coastal town of Onagawa trying to salvage any belongings he could from his ruined car. "People say it’s like a movie, but it’s been worse than any movie I’ve ever seen."

The official death toll stood at 10,151 Saturday, with more than 17,000 listed as missing, police said. With the cleanup and recovery operations continuing, the final number of dead was expected to surpass 18,000.

Officials have evacuated residents within 12 miles (20 kilometers) of the plant and advised those up to 19 miles (30 kilometers) away to stay indoors to minimize exposure. The U.S. has recommended that people stay 50 miles (80 kilometers) away from the plant.

Government spokesman Yukio Edano insisted that people living 12 to 20 miles (20 to 30 kilometers) 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 to places with better facilities.

"If the current situation is protracted and worsens, then we will not deny the possibility of (mandatory) evacuation," he said.

One Fukushima government official said some commercial trucks were refusing to enter the area because of radiation fears, resulting in a shortage of goods.

"We are not ordering people to leave. But we have told residents that we will help you leave voluntarily," Takeshi Ishimoto said.

Associated Press writers Elaine Kurtenbach, Tomoko A. Hosaka, Kristen Gelineau and Jean H. Lee in Tokyo and Jay Alabaster in Onagawa contributed to this report.