High radiation in water found at Unit 3 of the troubled Fukushima Daiichi nuclear plant may have originated at the reactor core, Japan's Nuclear and Industrial Safety Agency says.
So far, however, there is no evidence the containment vessel has been cracked or damaged, said agency spokesman Hidehiko Nishiyama, who appeared to be backing down slightly from a previous remark that there was a good chance the reactor had been damaged.
The statements came the day after three workers at the unit were hurt when they stepped into water found to be 10,000 times more radioactive than normal. Two suffered radiation burns and were taken to Fukushima Medical University Hospital, while the third didn't require treatment.
Japanese Prime Minister Naoto Kan sounded pessimistric in a televised address to the country Friday.
"The situation today at the Fukushima Daiichi power plant is still very grave and serious," Kan said. "We must remain vigilant. We are not in a position where we can be optimistic. We must treat every development with the utmost care."
He apologized to farmers and business owners around the plant for any damage He also thanked utility workers, firefighters and military personnel for "risking their lives" to cool the overheated facility.
The prime minister was speaking two weeks to the day after a magnitude-9.0 earthquake and subsequent tsunami set in motion unprecedented damage and explosions at the Daiichi nuclear site.
Uncertainty halted work at the overheated plant, where dozens of people had been trying to stop it from leaking dangerous radiation.
The high level of radiation in water at the site "could be a very dangerous and ominous sign, because if there is a breach, even a small one, radioactive material can begin to leak into the environment, [and] really change some of the parameters," reporter Steve Futterman told CBC News from Tokyo.