Four out of six reactors at the Fukushima Daiichi nuclear plant were damaged beyond repair in Japan’s devastating earthquake and tsunami, the chairman of the Tokyo Electric Power Co. said Wednesday.

Chairman Tsunehisa Katsumata also said he is taking over daily operations at Tokyo Electric, which owns the crippled plant, because the company’s president, Masataka Shimizu, has been hospitalized for an illness brought on by stress.

Shimizu, 66, has been largely silent since the March 11 earthquake and tsunami sent the Daiichi plant on a path toward nuclear disaster. Officials said Wednesday that he was suffering from hypertension and dizziness.

Also Wednesday, officials from the International Atomic Energy Agency urged the Japanese government to consider widening the evacuation zone around the facility. Recent radiation readings outside the exclusion zone show radiation substantially higher than levels at which the U.N. nuclear agency would recommend evacuations.

The comments could add to the debate over how far people need to stay away from the nuclear complex, whose cooling systems were crippled in the earthquake and tsunami.

Elena Buglova, an IAEA official, said radiation at the village of Iitate, about 25 miles from the Fukushima complex, “was about two times higher” than levels at which the agency recommends evacuations.

Japanese officials have told residents to evacuate within a 12-mile zone and to stay indoors within 18 miles of the damaged complex, but U.S. officials have recommended that American citizens stay at least 50 miles away.

The IAEA officials emphasized that the readings at Iitate were sporadic and only at one measuring point.

Denis Flory, a senior IAEA official, demurred when asked whether the agency was recommending that the village be cleared of residents but said it had advised Japanese authorities to “carefully assess the situation.”

Closer to the facility, contamination levels spiked offshore, and workers continued to endure soaring radiation levels as they labored to stave off a full-scale nuclear meltdown.

In the United States on Wednesday, the Environmental Protection Agency and the Food and Drug Administration announced that minuscule amounts of radioactive iodine-131 — probably from Fukushima — had been found in milk from Washington state. The amount detected was “more than 5,000 times lower” than the amount that would trigger FDA restrictions, the agency said.

Tokyo Electric’s stock price has plummeted, and Japanese lawmakers debated this week whether to nationalize the utility, which is Asia’s largest electric power company.

Katsumata, appearing before reporters Wednesday for the first time since the earthquake, said the company would prefer to remain privately held.

He expressed his “deep apology” for the “grave accident” at the plant and for the “anxiety, concern, and inconvenience caused to the society over the spread of radioactive substances to the atmosphere, water, and the impacts on crops and drinking water.”

He said that reactors No. 5 and 6 at the plant can still operate, but “we have no choice but to scrap” reactors 1 through 4. Estimates show that dismantling and decontaminating the site could take decades and cost upwards of $10 billion.

It is not the first time that Katsumata has dealt with a nuclear emergency as a result of a natural disaster. He was president of Tokyo Electric in 2007, when an earthquake struck a company-run power plant in Ni­igata prefecture, spilling hundreds of barrels of nuclear waste. In the aftermath, Katsumata had to apologize publicly for underreporting the extent of the damage. He was eventually moved from managing the day-to-day operations of the company into the chairman’s role.

Also on Wednesday, officials said measurements of radioactive iodine in the sea outside the Daiichi plant had spiked a day earlier, amplifying fears about an uncontrolled leak of highly contaminated water from at least one of the damaged reactors.

Levels of iodine-131 were 3,355 times the legal safety limit, up from the previous high of 1,850 times the limit that was recorded Sunday, officials said. The water was sampled about 1,000 feet south of a wastewater outlet.

“Experts are trying to analyze the situation and looking at all possibilities,” Yukio Edano, Japan’s chief cabinet secretary, said. “We are considering the worst-case scenario. If the radiation goes up and it affects health of people in the area, we will advise people immediately.”

Hundreds of engineers are working to bring the nuclear plant under control, including many consultants from other countries. The chief executive of the French nuclear energy company Areva arrived in Tokyo Wednesday, following a team of French engineers.

Potential solutions for containing the hazardous materials include spraying a synthetic resin on the ground to slow or stop contamination from spreading to the sea, and dropping a cloth cover over the reactors. Hydrogen explosions blew off the roofs of two reactors and damaged a third; at least one reactor’s spent fuel pools are now exposed to the environment.

Hironobu Unesaki, professor of nuclear engineering at Kyoto University, said a cover, fit with a customized ventilation system, could be an effective way to control gaseous emissions from the reactors. But he said it would likely not have an impact on the water leaking from a pipe or a compression chamber at the base of the reactor, as the company suspects is happening.

Workers made limited progress Wednesday in eliminating radioactive water from the cavernous turbine rooms next to the first three nuclear reactors.

Water in two of the buildings has not yet been drained, because nearby condenser tanks needed to receive the water are already full. It could take several days to empty their contents safely into another tank on-site.

In the room adjacent to the first reactor, workers were able to reduce knee-deep water to a depth of about eight inches. But work stalled because the condenser tank there became full. Government officials Wednesday raised the possibility of using a tanker or large boat as a repository for the contaminated water.

Water-based radiation in the building outside the second reactor exceeds 1,000 millisieverts per hour, or 100,000 times the level that would be found if the plant were operating normally.

Also on Wednesday, Japan’s Emperor Akihito and Empress Michiko visited an evacuation center in Tokyo. The rare public visit followed the emperor’s first-ever televised address a week earlier, underscoring the gravity of the country’s situation.

Correspondent Andrew Higgins and special correspondents Tetsuya Kato and Akiko Yamamoto in Tokyo and staff writer Brian Vastag in Washington contributed to this report.