The Nuclear and Industrial Safety Agency, or NISA, said TEPCO was aware there was high radiation in the air at one of the plant's six units several days before the accident. And the two workers injured were wearing boots that only came up to their ankles hardly high enough to protect their legs, agency spokesman Hidehiko Nishiyama said.
"Regardless of whether there was an awareness of high radioactivity in the stagnant water, there were problems in the way work was conducted," Nishiyama said.
NISA warned TEPCO to improve and ensure workers' safety, and TEPCO has taken measures to that effect, Nishiyama said, without elaborating.
TEPCO spokesman Hajime Motojuku declined to comment.
The government's admonishments came as workers at the plant struggled to stop a troubling rise in radioactivity and remove dangerously contaminated water from the facility, which has been leaking radiation since a massive earthquake and tsunami on March 11 knocked out the plant's key cooling systems. Officials have been using seawater to try to cool the plant, but fears are growing that the corrosive salt in the water could further damage the machinery inside the reactor units.
TEPCO is now rushing to inject the reactors with fresh water instead, and to begin extracting the radioactive water, Nishiyama said.
Defense Minister Yoshimi Kitazawa said late Friday that the U.S. government had made "an extremely urgent" request to switch to fresh water. He said the U.S. military was sending water to nearby Onahama Bay and that water injections could begin in the next few days.
The U.S. 7th Fleet confirmed that barges loaded with 500,000 gallons of fresh water supplies were on their way.
The situation at the crippled complex remains unpredictable, Edano said Saturday, adding that it would be "a long time" until the crisis ends.
"We seem to be keeping the situation from turning worse," he said. "But we still cannot be optimistic."
Efforts to get the nuclear plant under control took on fresh urgency this week when nuclear safety officials said they suspected a breach in one or more of the plant's units possibly a crack or hole in the stainless steel chamber around a reactor core containing fuel rods or the concrete wall surrounding a pool where spent fuel rods are stored.
Such a breach could mean a much larger release of radioactive contaminants.
Radioactivity was on the rise in some units, Nishiyama said Saturday.
"It is crucial to figure out how to remove contaminated water while allowing work to continue," he said, acknowledging that the discovery would set back delicate efforts to get the plant's cooling system operating again.
Workers have begun pumping radioactive water from one of the units, Masateru Araki, a TEPCO spokesman, said Saturday.
Plant officials and government regulators say they don't know the source of the radioactive water. It could have come from a leaking reactor core, connecting pipes, or a spent fuel pool. Or it may be the result of overfilling the pools with emergency cooling water.
But a breach in the chamber surrounding the reactor core seemed "more likely," Nishiyama said.
TEPCO said late Saturday that a trace of radioactive water had leaked from the Unit 2 reactor building into a sewage line. It was not clear if the source of the water was the same as the other leakage. TEPCO said officials were investigating.
Radiation has been seeping from the plant since the magnitude-9 earthquake and tsunami struck more than two weeks ago. Since then, it has made its way into milk, seawater and 11 kinds of vegetables, including broccoli, cauliflower and turnips.
Tap water in several areas of Japan, including Tokyo, has shown higher-than-normal levels of radiation. In the capital, readings were at one point two times higher than the government safety limit for infants, who are particularly vulnerable to radioactive iodine.
But levels have fallen steadily since peaking Wednesday, and Tokyo metropolitan officials said Saturday that tap water was safe for babies to drink.
Just outside a reactor at the coastal nuclear plant, radioactivity in seawater tested about 1,250 times higher than normal, Nishiyama said. He said the area is not a source of seafood and the contamination posed no immediate threat to human health.
However, tests conducted 18 miles (28 kilometers) offshore found radioactive iodine-131 at levels nearing the regulatory limit set by the Japanese government, the International Atomic Energy Agency said. The tests also detected another radioactive substance, cesium-137, at lower levels.
IAEA experts said the ocean will quickly dilute the worst contamination. Radioactive iodine breaks down within weeks but cesium could foul the marine environment for decades.
The nuclear crisis has added to the misery and uncertainty facing Japan in the wake of the disastrous earthquake and tsunami.
Japanese soldiers and U.S. Marines were clearing away debris so they could keep searching for bodies and bury the dead. The official death toll was 10,418 Saturday, with more than 17,000 listed as missing, police said. Those lists may overlap, but the final death toll was expected to surpass 18,000.
Overwhelmed by bodies along the coast, government officials conducted more mass burials Saturday. In Yamamoto, relatives wailed and yelled their farewells as the first 11 caskets were buried in one end of a long mass grave in a vegetable patch, with at least 400 more burials planned in the coming days.
In Higashimatsushima, soldiers lowered plywood coffins into a ditch dug at a recycling plant as freezing rain fell on mourners weeping quietly under umbrellas. Funerals in Japan are a highly formalized Buddhist ceremony, and the mass burials are yet another tragedy for the hard-hit coastal towns.
The misery has extended to the hundreds of thousands whose homes were destroyed, many of whom now sleep on crowded school gymnasium floors with few comforts. Those living within a 12-mile (20-kilometer) radius of the plant have been evacuated.
Life was also tough in the ghost towns inside a larger voluntary evacuation zone, with most residents choosing to flee and wary truckers refusing to deliver goods.
In Minamisoma, a city of 71,000 about 20 miles (30 kilometers) north of the plant, all but one or two shops shut their doors because of a lack of goods and customers, city official Sadayasu Abe said.
"Commercial trucks are simply not coming to the city at all due to radiation fears," he said.
Military troops and some private companies took up the task of delivering rice, instant noodles, bottled water and canned foods to eight central spots in the city, Abe said.
He said the city was urging the 10,000 or so still remaining to leave since the situation at the plant remains precarious.
"Life is very difficult here," he told The Associated Press by telephone. "We have electricity, gas and running water, but no food."
Muneyuki Munakata, a 58-year-old firefighter who was evacuated from his home near the plant, has been living in a shelter about 25 miles (40 kilometers) west of the nuclear complex for 15 days. Evacuees have plenty of instant noodles, but not enough rice or fuel for the stove, he said.
"People here are all exhausted," he said. "We all talk about when we can go home, but I don't know when because of uncertainty over the nuclear disaster."
Yamaguchi reported from Tokyo, as did Associated Press writers Shino Yuasa, Kristen Gelineau, Jeff Donn, Mayumi Saito and Joji Sakurai. Jay Alabaster contributed to this report from Yamamoto.