As the death toll from Japan's earthquake and tsunami swells ever closer to 10,000, engineers continue to hit roadblocks in their race to bring the hobbled Fukushima Daiichi nuclear power plant under control.

Today, engineers discovered that crucial machinery at one reactor will need to be repaired, a process that will take two to three days, according to government officials.

Another team of workers laboring on a separate reactor was evacuated in the afternoon after gray smoke rose from reactor No. 3, said Tetsuro Fukuyama, deputy chief cabinet secretary. They heard no explosion, though, and the smoke ended by 6 p.m., according to news reports by NHK.

In a separate incident, NHK said that the Japanese Nuclear and Industrial Safety Agency reported white smoke was coming from the reactor No. 2 building.

Neither of those incidents appears to have produced significantly higher levels of radiation.

Meanwhile, the U.S. State Department said it would offer potassium iodide to its staff members and dependents in Japan as a precaution against possible radiation exposure. However, its online travel warning advised against taking the compound "at this time."

Hundreds of employees from the Tokyo Electric Power Co., which owns the Fukushima power station, worked through the weekend to connect a mile-long high-voltage transmission line to reactor No. 2, hoping to restart a cooling system that would help bring down the temperature in the reactor and spent fuel pool.

They connected the transmission line yesterday, but today discovered that they still did not have enough power to fully run the systems, officials from the Japanese nuclear safety agency said.

Engineers are also hoping to today finish repairing the ventilation system in the control room used to monitor the No. 1 and No. 2 units. When the repairs are done, they will begin cleansing the air so that workers can eventually return and begin using the equipment inside to monitor the conditions at the two reactors.

Firefighters from Tokyo sprayed water on Reactor No. 3 overnight, and firetrucks from the Japan Self-Defense Forces and the American Army spent two hours dousing reactor No. 4 this morning.

But nuclear safety agency officials said some of the water used in the operations had reached the ocean nearby, and officials are now testing radiation levels in the water.

Separately, high levels of radioactive elements were detected in the water supply of Iitate village, about 30 miles from the plant, and residents were ordered not to drink the tap water, said Takashi Hashiguchi, a Health Ministry official.

That order came a day after the government barred all shipments of milk from Fukushima prefecture and shipments of spinach from Ibaraki prefectureafter finding above-normal levels of radioactive elements.

Peter Cordingley, a spokesman for the World Health Organization, said that the discovery of radiation in food was a more serious problem than the organization had initially expected.

Cordingley said there was no evidence that contaminated food had reached export markets, but "it's a lot more serious than anybody thought in the early days when we thought that this kind of problem can be limited to 20 to 30 kilometers," he told Reuters (Belson/Tabuchi/Onishi, New York Times, March 21). -- AS