TOKYO — Working overnight into today, engineers successfully restored power to cooling pumps in two reactors at the disabled Fukushima Dai-ichi nuclear power plant, the first genuinely hopeful sign in the weeklong battle to prevent a meltdown at any of the six reactors at the site.
The positive development was preceded by grimmer reports of possible risks to the food supply.
Although power has so far been restored only at reactor buildings 5 and 6, which were not considered a particular threat, that success suggests that workers are finally beginning to make some headway in their effort to prevent more radiation from escaping the plant.
The two reactors had been shut down at the time the magnitude 9 earthquake struck a week ago, but spent fuel rods in an upper level of the reactor buildings were still generating heat and required cooling. When electricity at the site was lost and the tsunami damaged backup generators, the pools holding the fuel rods began to grow warmer.
Officials of the Tokyo Electric Power Co., which owns the plant, said water in the No. 5 pool had already cooled by about 10 degrees Fahrenheit since the cooling pumps had started working.
Engineers said they hoped to have the power connected to the remaining reactor buildings sometime today or early Monday.
But in gloomier news Saturday, the government said it found higher-than-normal levels of radioactive materials in spinach and milk at farms up to 90 miles away from the ravaged nuclear power plants, the first confirmation by officials that the unfolding nuclear crisis has affected the nation's food supply.
Chief Cabinet Secretary Yukio Edano said spinach and milk were the only products found with abnormally high levels of radioactive materials. The newly discovered radioactivity contained in the average amount of spinach and milk consumed in an entire year would be equal to the amount received in a single CAT scan, he said.
"These levels do not pose an immediate threat to your health," Edano said, adding that the Health, Labor and Welfare Ministry would provide additional details. "Please stay calm."
Asparagus, cucumbers, radishes, tomatoes and other vegetables are also grown in Fukushima, but have not been found to be contaminated, officials said.
The Fukushima prefecture asked dairy farms within 18 miles of the nuclear plant on Saturday to halt all milk shipments. The milk that contained higher levels of radioactive material was tested at farms about 19 miles from the hobbled nuclear plants in Fukushima prefecture. The spinach was found in Ibaraki prefecture, at farms 60 to 90 miles south of the plants.
Food safety inspectors said the amount of iodine-131 found in the tested milk was five times higher than levels deemed safe. They said the iodine found in the spinach was more than seven times higher. The spinach also contained slightly higher amounts of cesium-137.
Iodine-131 and cesium-137 are two of the most dangerous elements that are feared to have been released from the plants in Fukushima. Iodine-131 can be dangerous to human health, especially if absorbed through milk and milk products, because it can accumulate in the thyroid and cause cancer. Cesium-137 can damage cells and lead to an increased risk of cancer.
This report contains information from the Los Angeles Times and New York Times.