The US Food and Drug Administration blocked the import from China of five species of seafood, as there is a health threat of contamination with unsafe drugs.

The FDA announced Friday that it would block the import of certain Farm-raised seafood species from China until they are “proven to be free of residues from drugs that are not approved in the United States for use in farm-raised aquatic animals.”

The species concerning the FDA are shrimp, catfish, basa (a type of catfish), dace (a type of carp) and eel. Repeated analysis from October 2006 to May 2007 showed contamination with antimicrobials and antibiotics like nitrofuran, malachite green, gentian violet and fluoroquinolones.

No illnesses have been reported to date and the FDA said levels of the drugs are extremely low, “most often at or near the minimum level of detection.”

The statement said: “The use of fluoroquinolones in food animals may increase antibiotic resistance to this critically important class of antibiotics.” It added that the fish products would not be recalled because of the low levels of drugs found.

“Chinese officials have acknowledged that fluoroquinolones are used in Chinese aquaculture and are permitted for use in China,” the FDA said. However, the US will not resume importing the seafood until Chinese authorities not prove the safety of the fish.

Nitrofuran, malachite green and gentian violet are known or suspected carcinogens, the FDA said.