"The FDA will start to detain these products at the border until the shipments are proven to be free of residues from drugs that are not approved in the United States for use in farm-raised aquatic animals," said the agency in a statement.

The FDA, a part of the US Department of Health and Human Services, said the action will "protect American consumers from unsafe residues that have been detected in these products," but it also noted that there have been no reports of illnesses to date.

The FDA action includes conditions under which an exporter can be exempted from FDA's detention action by providing specified information to the agency.

This information must demonstrate the exporter has implemented steps to ensure its products do not contain these substances and that preventive controls are in place. The additional import controls placed on seafood from China will last as long as needed, said the statement.

The FDA may allow the entry into the United States and subsequent distribution into the marketplace of individual shipments of the Chinese farm-raised seafood products if the company provides documentation to confirm the products are free of residues of these drugs.

"We will accept entries of these products from Chinese firms that demonstrate compliance with our requirements and safety standards," said Dr. David Acheson, FDA's assistant commissioner for food protection.