Federal health officials has ordered dozens of imported foods from China held at the border as possible health risks.
Most are ethnic treats, including snacks, drinks and chocolates.
It is unusual for the Food and Drug Administration to put such a broad hold on goods from an entire country, not just a few rogue manufacturers. The agency said the order, which covers products made with milk, was needed as a precaution to keep out foods contaminated with the industrial chemical melamine, which can cause serious kidney problems.
"The problem of melamine contamination in Chinese food products is a recurring one," said the FDA order, posted on the Internet.
Under the directive, FDA inspectors can hold foods made with milk ingredients at ports of entry until independent tests show they are melamine-free. The order also applies to pet foods and some bulk protein products.
"We've continued to get information from others in the international community, and reports from China, about (melamine contamination) moving into different commodities," said Steve Solomon, a senior FDA enforcement official.
"Most of the products we are talking about are finished products like cookies, cakes and candies. The impact will be for various ethnic communities looking for specific products."
Under the directive, FDA inspectors at US ports of entry will detain foods from China made with milk and certain ingredients derived from milk. Importers must pay to have their products tested by independent laboratories that meet FDA standards. Only products found to be melamine-free will be allowed into the country.
The order also applies to pet foods and some bulk protein products, the focus of a melamine recall in 2007.
Essentially, the FDA action shifts the burden of proof to Chinese companies, which must now supply evidence that their products are safe. Most American consumers should not be affected, because major US food manufacturers get their milk ingredients in the United States.
Unscrupulous companies in China have routinely watered down milk, then added melamine to artificially boost protein readings on quality tests. The practice became known after the Beijing Olympics this summer. It backfired when tens of thousands of Chinese children got sick with kidney problems after drinking contaminated infant formula. Nearly 13,000 children were hospitalised in China, and at least four died.
Other melamine-tainted products soon surfaced, setting off a global safety scandal that has further tarnished the reputation of Chinese brands.
The US does not import milk or infant formula from China, and no illnesses have been reported here. But authorities from California to Connecticut have found melamine-contaminated candies and drinks during inspections at Asian groceries. Thursday's FDA order widens a directive from last month authorising inspectors to detain goods from 10 Chinese companies.
"The problem of melamine contamination (in China) is not limited to infant formula products," said the FDA order.
"Chinese government sources indicate contamination of milk components, especially dried milk powder, which are used in a variety of finished foods. These contaminated milk components appear to have been dispersed throughout the Chinese food supply chain."
The melamine scandal is now weeks old, but FDA officials said it has taken that long to comply with legal requirements that detention orders be scrupulously backed by evidence.
A national poll released earlier this week by Consumers Union found that the public wants foreign food-producing facilities inspected as frequently as domestic ones: about once a month. The FDA has nowhere near the number of inspectors to fulfill that desire, and instead mainly relies on US food companies to require that their foreign supplier maintain high standards.
