Workers are attempting to remove the radioactive water from the tsunami-ravaged nuclear compound and restart the regular cooling systems for the dangerously hot fuel.

The day began with company officials reporting that radiation in leaking water in the Unit 2 reactor was 10 million times above normal, a spike that forced employees to flee the unit. The day ended with officials saying the huge figure had been miscalculated and offering apologies.

"The number is not credible," said Tokyo Electric Power Co. spokesman Takashi Kurita. "We are very sorry."

A few hours later, TEPCO Vice President Sakae Muto said a new test had found radiation levels 100,000 times above normal — far better than the first results, though still very high.

But he ruled out having an independent monitor oversee the various checks despite the errors.

Officials acknowledged there was radioactive water in all four of the Fukushima Dai-ichi complex's most troubled reactors, and that airborne radiation in Unit 2 measured 1,000 millisieverts per hour, four times the limit deemed safe by the government.