It has apparently been leaking contaminated water into the ocean for the two years since the earthquake/tsunami disaster that saw three of the plant's six reactors suffer a meltdown, Shunichi Tanaka, head of Japan's Nuclear Regulation Authority said Wednesday.
Ground water leaking into the basement of the damaged reactors is becoming contaminated and has to be pumped out and stored in huge tanks on site, but the inflow has not yet been stopped, officials said.
Tanaka said neither authority staff nor those working for the plant's operator have been able to determine where the leaks are coming from, the Christian Science Monitor reported.
Plant operator Tokyo Electric Power, which has constantly denied any of that water has been leaking into the ocean, has admitted in the last few days it can't actually say for sure that the water is not leaking into the sea.
Tanaka said the evidence strongly suggests such leaking.
"We've seen for a fact that levels of radioactivity in the seawater remain high, and contamination continues -- I don't think anyone can deny that," he said. "We must take action as soon as possible."