SENDAI, Japan – Japan’s government revealed a series of missteps by the operator of a radiation-leaking nuclear plant Saturday, including sending in workers without protective footwear in its faltering efforts to control a monumental crisis.

The U.S. Navy, meanwhile, rushed to deliver fresh water to replace corrosive saltwater now being used in a desperate bid to cool the plant’s overheated reactors.

Government spokesman Yukio Edano urged Tokyo Electric Power Co. to be more transparent, two days after two workers at the tsunami-damaged Fukushima Dai-ichi plant suffered skin burns when they stepped in water that was 10,000 times more radioactive than levels normally found near the reactors.

“We strongly urge TEPCO to provide information to the government more promptly,” Edano said.

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.

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 during the last 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, said Masateru Araki, a TEPCO spokesman.

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 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 Saturday so they could keep searching for bodies and bury the dead. The official death toll was 10,418 , with more than 17,000 listed as missing.