Authorities discovered radioactive water from the damaged Fukushima Daiichi nuclear power plant flowing into the sea from a crack in the No. 2 reactor Saturday, adding to mounting problems facing emergency repair workers a day after Japan’s prime minister tried to shift the country’s attention toward reconstruction.

A crack measuring almost eight inches long was discovered in the concrete wall of a pit where power cables are stored, according to Tokyo Electric Power Co. (Tepco), the plant’s owner. The area above where the water was pooling and leaking into the ocean had a radioactivity reading of 1,000 millisieverts per hour.

The maximum radiation level to which workers can legally be exposed is 250 millisieverts per hour.

Hidehiko Nishiyama, deputy director general of Japan’s Nuclear and Industrial Safety Agency, said his agency has instructed Tepco to search the facility for other potential leaks.

“Today we found highly irradiated water in the pit where the electricity cables are contained,” Nishiyama said. “It seems that there is a crack on the side of the concrete wall of the pit. Some water is spilling out of the crack to the sea.”

At a news conference Saturday, a Tepco spokesman said the company plans to pour concrete into the crack to try to stop the leak.

The discovery came as Tepco was considering broader steps to deal with the burgeoning crisis. Among the latest ideas, officials said, are pumping nitrogen into reactors Nos. 1 and 3 to try to prevent explosions of hydrogen gas that is building up and using an artificial floating island to store contaminated water that has pooled inside the facility.

The reactors, when operating properly, are filled with nitrogen. Officials fear the nitrogen level might have decreased during explosions inside the power plant during the early days of the crisis, after the March 11 earthquake and tsunami knocked out the critical cooling systems.

As Tepco continued to struggle to contain the radiation leaks, a 15-member advance team from the U.S. military’s radiation control unit arrived at Yokota Air Base. Kyodo News reported that 140 more Marines from the unit are on the way. The force can monitor radiation levels, help with search-and-rescue operations and deal with decontamination, the wire service reported.

On Friday, Prime Minister Naoto Kan addressed his nation three weeks after the “Great East Japan Earthquake” to say that although disaster relief continues, the government will now begin focusing its attention on reconstruction, building a “bright and promising future.”

Even as he spoke, U.S. and Japanese military troops and rescue workers joined forces to launch an intensive three-day search for the missing, whose numbers still exceed 16,000.

The operation involved at least 25,000 rescuers, 120 airplanes and 65 ships. They are combing marshes along coastlines where the giant waves washed away whole towns and villages, and teams of divers are fanning out into the ocean. A total of 32 bodies were recovered Friday, according to the Kyodo news service.

Kan visited the disaster zone Saturday and went to shelters and a staging area inside the evacuation zone for emergency workers at the Fukushima Daiichi plant. Engineers and firefighters are working in dangerous conditions to try to stabilize the plant.

The area around the site remains volatile as highly radioactive water continues to leak from at least one reactor. On Friday, Tepco reported the contamination levels in the groundwater outside the unit 1 reactor far exceeded the legal limit, adding the area to a growing list of high-risk hot spots on the site.

The exact levels were unclear. The utility said some of its original measurements were wrong.

The utility said radioactive iodine levels there were 10,000 times the safety limit. But it retracted previous reported readings for other elements, including zirconium and tellurium, saying they were flawed.

Hidehiko Nishiyama, deputy director general for the Nuclear and Industrial Safety Agency, ordered a review of the company’s radiation data, warning that such errors “undermine the credibility” of their assessments. It’s the second time Tepco has retracted information about radiation levels.

Insufficient monitoring has become a pressing safety issue at the plant. Nuclear regulators warned Tepco on Friday that every worker must wear a radiation-monitoring dosimeter to keep track of exposure.

The warning came in response to a revelation Thursday by company officials that most of their dosimeters had been destroyed by the tsunami. Sometimes only group leaders were given a badge. Tepco officials on Friday said they had obtained more badges and that all workers would wear one.

The utility said Friday that 21 workers exceeded a cumulative exposure level of 100 millisieverts but that no one has exceeded the maximum allowed limit of 250 millisieverts. The number of people on-site each day ranges from about 350 to 1,000, government and Tepco data show.

Workers could receive a maximum dose in 15 minutes in some parts of the plant, where levels exceed 1,000 millisieverts per hour. To stay within those limits, workers must avoid large areas of the site and work in rotating shifts, one of the reasons progress remains slow.

Kan said that once the plant becomes more stable, the government will begin “a very thorough investigation” of what systems broke down, as well as a reevaluation of the country’s nuclear energy policies.

Kan said any future policies would put disaster preparation as a top priority.

“We will have measures in place to prepare ourselves for any possible scenario,” he said.

Speaking on the first day of the new fiscal year, Kan said parliament would begin crafting a supplementary budget to fund long-term reconstruction. He announced an April 11 conference for specialists and local government officials to develop a vision for rebuilding.

He said at a news conference that one of the ideas they would discuss was creating an innovative “ecotown” that would become a model for others. Local officials also want housing for those working in fisheries companies and at the ports to be moved to higher hills.

More than 166,000 Japanese are still displaced from their homes, according to the National Police Agency. Slowly, life is resuming a semblance of routine for some students who are getting ready to start school again in temporary buildings and adults who are returning to work, even while commuting from temporary homes on gymnasium floors.

Special correspondent Akiko Yamamoto contributed to this report.