The FDA has announced that it will detain all dairy products, fruits, and vegetables originating in the vicinity of Japan's damaged atomic energy complex that was heavily damaged in the March 11 earthquake and tsunami.
Foods exported from the area may contain radioactive particles, after tests in Japan showed that milk, spinach, and other vegetables from in and around Fukushima prefecture had potentially dangerous levels of radiation.
The agency plans to quarantine any such products entering U.S. ports and prevent their distribution, an FDA spokesperson said.
Releases of radioactive particles from reactor buildings at the Fukushima Daiichi nuclear station on Japan's northeast coast have continued for more than a week.
A series of explosions and deliberate releases have sent clouds of radioactive particles billowing from the plant since early last week.
Japanese authorities initially downplayed the risk of food contamination, but radiation has been detected in agricultural products from the general area of the plant.
In a terse situation update issued Monday, the World Health Organization (WHO) said "low-level contamination of drinking water" had been confirmed as well.
The Wall Street Journal reported Tuesday that elevated radiation levels had been detected in water supplies serving five towns near the plant. It said the Japanese government had characterized the short-term health risk as negligible but also advised residents to avoid giving the water to infants.
On Monday, the government stopped shipments of spinach and other types of leafy produce from four prefectures (roughly corresponding to counties in the U.S.) around the nuclear site.
Sales of fresh dairy products from Fukushima prefecture were also halted.
Milk samples from Fukushima were found to have iodine-131 levels that were 17 times higher than the maximum allowed by law, according to the Wall Street Journal.
U.S. officials have continued to say that significant contamination of foods on this side of the Pacific Ocean was highly unlikely, because radioactive particles emanating from the Japanese facility would be dispersed into the vastness of the atmosphere and ocean.
"At this time, there is no public health threat in the U.S. related to radiation exposure," according to a statement posted Monday on the FDA's website and still featured prominently late Tuesday.
"FDA, together with other agencies, is carefully monitoring any possibility for distribution of radiation to the United States. At this time, theoretical models do not indicate that significant amounts of radiation will reach the U.S. coast or affect U.S. fishing waters."
The agency added that the Environmental Protection Agency was tracking the drift of radiation to the U.S. -- already detected but at levels far below those believed to pose a health risk. The FDA also promised that it would take action if its own monitoring showed that accumulation in domestic dairy products or other foods had become significant.
Concern about foods -- and other products -- imported from Japan had already become international. Many of the country's Asian trading partners have stepped up screening of Japanese agricultural exports or, like the U.S., stopped imports from Japan altogether.
The WHO said it was working with officials from the U.N.'s Food and Agriculture Organization (FAO) to monitor the situation.
The FAO, in turn, noted that it has had an ongoing joint program with the International Atomic Energy Agency addressing the threats to food supplies from radiological events like the one now occurring in Japan.
Primarily, the agencies develop guidelines and standards. The FAO said it could send teams of specialists to event locations to provide "analytical services," but did not indicate whether it had done so in Japan.