The frozen shrimp, catfish and eel arrived at U.S. ports under an "import alert," which meant the FDA was supposed to hold every shipment until it had passed a laboratory test.
But that was not what happened, according to an AP check of shipments since last fall. One of every four shipments the AP reviewed got through without being stopped and tested. The seafood, valued at $2.5 million, was equal to the amount 66,000 Americans eat in a year.
FDA officials stuck the pond-raised seafood on their watch list because of worries it contained suspected carcinogens or antibiotics not approved for seafood.
No illnesses have been reported, but the episode raises serious questions about the FDA's ability to police the safety of America's food imports.
"The system is outdated and it doesn't work well. They pretend it does, but it doesn't," said Carl R. Nielsen, who oversaw import inspections at the agency until he left in 2005 to start a consulting firm, FDAImports.com. "You can't make the assumption that these would be isolated instances."
If the system cannot stop known risks, Nielsen said, how can it protect against hidden dangers, such as the ingredients from China that made toothpaste potentially poisonous and killed dozens of pets earlier this year?
"The FDA itself admits that this seafood needs inspection, but then doesn't have the capability to inspect it," Democratic Sen. Charles Schumer, a critic of the FDA's food safety record, said in reaction to the AP's findings. "This is an example of government failure at its worst."
China is America's biggest foreign source of seafood, the 1.06 billion pounds it supplied in 2006 accounting for 16 percent of all seafood Americans buy.
President George W. Bush has asked a Cabinet-level panel to recommend better imported food safety safeguards. Chinese officials have promised to inspect fish farms closely for the use of drugs and chemicals, even as they called the FDA's testing mandate illegal under world trade rules.
FDA officials acknowledged that some shipments slip through import alerts, but said overall they work.
"Any time you introduce a human element into something, I don't think you can necessarily guarantee 100 percent," said Michael Chappell, the official responsible for field inspections and labs.