TOKYO (AP) -- A suspected breach in the core at one reactor at a stricken Fukushima nuclear plant could mean more serious radioactive contamination, Japanese officials revealed Friday -- a situation the prime minister called "very grave and serious."
A somber Prime Minister Naoto Kan sounded a pessimistic note at a briefing hours after nuclear safety officials said they suspected a breach at the Fukushima Dai-ichi plant that would be a major setback in the urgent mission to stop the facility from leaking radiation.
"The situation today at the Fukushima Dai-ichi power plant is still very grave and serious. We must remain vigilant," Kan said. "We are not in a position where we can be optimistic. We must treat every development with the utmost care."
The uncertain situation halted work at the nuclear complex, where dozens had been trying feverishly to stop the overheated plant from leaking dangerous radiation. The plant has leaked some low levels of radiation, but a breach could mean a much larger release of contaminants.
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 milk and produce were found to contain elevated levels of radiation.
The prime minister also thanked utility workers, firefighters and military personnel for "risking their lives" to cool the overheated facility.
The alarm Friday comes on a day marking two weeks since the magnitude-9 quake triggered a tsunami that enveloped cities along the northeast coast and knocked out the Fukushima reactor's cooling system.
Police said the official death toll jumped past 10,000 on Friday. 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.
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.