A suspected breach in the reactor core at one unit of a stricken Fukushima nuclear plant could mean more serious radioactive contamination, Japanese officials said Friday, revealing what may prove a major setback in the mission to bring the leaking plant under control.

The uncertain situation halted work Friday at the Fukushima Dai-ichi nuclear complex, where dozens had been working feverishly to stop the overheated plant from leaking dangerous radiation, officials said.

Suspicions of a possible breach were raised when two workers waded into water 10,000 more radioactive than normal and suffered skin burns, the Nuclear and Industry Safety Agency said. Continue reading.