TOKYO - A Japanese utility said Monday its crippled Fukushima nuclear plant is likely leaking contaminated water into the sea, acknowledging for the first time a problem long suspected by experts.
Tokyo Electric Power Co., which operates the Fukushima Dai-ichi plant, also came under criticism Monday for not disclosing earlier that the number of plant workers with thyroid radiation exposures exceeding threshold levels for increased cancer risk was 10 times what it said earlier.
The delayed announcements underscored the criticism the company has faced over the crisis, caused by a 2011 tsunami. TEPCO has been repeatedly blamed for overlooking early signs, and covering up or delaying the disclosure of problems and mishaps.
Company spokesman Masayuki Ono said at a news conference that plant officials have come to believe that radioactive water that leaked from the wrecked reactors is likely to have seeped into the underground water system and escaped into the sea.
Nuclear officials and experts have suspected a leak from the Fukushima Dai-ichi since early in the crisis. Japan's nuclear watchdog said two weeks ago a leak was highly suspected and ordered TEPCO to examine the problem.
TEPCO had persistently denied contaminated water reached the sea, despite spikes in radiation levels in underground and seawater samples taken at the plant. The utility first acknowledged an abnormal increase in radioactive cesium levels in an observation well near the coast in May and has since monitored water samples.
Ono said plant officials believe a leak is possible because the underground water levels in suspected areas fluctuate in accordance with tide movements and rainfalls.
"We are very sorry for causing concerns. We have made efforts not to cause any leak to the outside, but we might have failed to do so," he said.
Ono said the radioactive elements detected in water samples are believed to largely come from initial leaks that have remained since earlier in the crisis. He said the leak has stayed near the plant inside the bay, and officials believe very little has spread farther into the Pacific Ocean.
TEPCO is currently injecting a chemical solution into the coastline embankment to solidify underground structures and block contaminated underground water from escaping into the sea - an operation revealed to the Japanese media Monday.
Marine biologists have warned that the radioactive water may be leaking continuously into the sea, citing high radioactivity in fish taken near the plant.