The Food and Drug Administration has announced broader import control of all farm-raised catfish, basa, shrimp, dace, and eel from China.

The FDA is taking the action because the agency repeatedly found that seafood products from China contained antimicrobials that the agency has not approved for use in farm-raised aquatic animals in the United States. Starting June 28, the FDA began detaining the seafood products until the exporters could prove the shipments to be free of the drug residues.

The contaminants in question are the antimicrobials nitrofuran, malachite green, gentian violet, and fluoroquinolone. Research has shown the first three drugs to be carcinogenic with long-term exposure in laboratory animals. Use of fluoroquinolones in food animals might increase antimicrobial resistance, according to the FDA.

Chinese authorities also prohibit nitrofuran and malachite green in aquaculture, though they permit fluoroquinolones.

The concentrations of the drug residues in the seafood products are low, most often at or near the minimal level of detection. The FDA is not seeking recall of products already in U.S. commerce and is not advising consumers to destroy or return products they may have in their homes. The agency's concern is for long-term exposure as well as the possible development of antimicrobial resistance.

The FDA might allow entry into the United States of individual shipments of farm-raised seafood products from China if the exporter provides documentation confirming that the products are free of the drug residues in question.