The Canadian-made meal included what was purported to be wheat gluten, a protein source, imported from China. The material was actually wheat flour spiked by the chemical melamine and related, nitrogen-rich compounds to make it appear more protein rich than it was, officials said.
After pigs and chickens, the farmed fish mark the third food animal given contaminated feed. The level of contamination is expected to be too low to pose any danger to human health, said Dr. David Acheson, the FDA's assistant commissioner for food protection.
It wasn't immediately clear if any of the farmed fish entered the food supply. However, Acheson said at least one firm's fish were still too young and small to be sold. Investigators were visiting other U.S. aquaculture farms that used the contaminated feed. Farmed fish typically are sold for direct consumption or for stocking lakes and streams.
Melamine, a chemical found in plastics and pesticides and not approved for use in pet or human in the U.S., contaminated pet food that either sickened or killed an unknown number of dogs and cats. Since March 16, more than 100 brands of pet food have been recalled because they were contaminated with melamine.
Acheson said that fish samples would be screened for signs of melamine. "Depending upon what we find in that testing, that is going to drive the next steps," Acheson said.
Canadian officials are aware of the finding, Acheson said.
"We used it to make pet food. They used it to make fish meal," he told reporters.
Federal health and food officials have said some 20 million chickens and thousands of hogs also were fed feed contaminated by melamine. As with the fish, they said the risk to human health is very low.
U.S. investigators also have learned that the purported Chinese wheat gluten and a second ingredient, rice protein concentrate, were actually simple wheat flour. The flour was spiked with melamine and related, nitrogen-rich compounds to make it appear more protein rich than it was. In tests, nitrogen levels are measured to gauge the overall protein content of food ingredients.
"What we discovered is these are not wheat gluten and rice protein concentrate but in fact are wheat flour contaminated by melamine," Acheson said.
The FDA is considering enforcement options, he added. The ingredients came from two Chinese firms: Xuzhou Anying Biologic Technology Development Co. and Futian Biology Technology Co. Ltd.
The supposed wheat gluten was exported directly from China to Canada in a deal brokered by a U.S. company, ChemNutra Inc., Acheson said. ChemNutra also supplied the ingredient to a Canadian dog and cat food company, Menu Foods, that's since recalled dozens of brands.
Steve Stern, a ChemNutra spokesman, said the Las Vegas company actually only cobrokered the deal to supply wheat gluten to the fish meal producer: "We never owned it, we never sold it."
When asked why the company didn't disclose previously that it had had a part in that deal, Stern said: "I really haven't got an answer to that right now."
Menu Foods has said it faces more than 50 lawsuits. It in turn has sued ChemNutra. And the FDA has searched facilities belonging to both companies.