There is no evidence that any of the two contaminated batches of wheat gluten and rice protein from China ended up as an ingredient in human food, "but it's prudent to look," said Dr. David Acheson, assistant FDA commissioner for food protection.
Acheson said the inspections began this week, covering both human and pet food manufacturers to raise awareness of how important it is to know their supply chain and to make sure none of the contaminated products remain in stock.
The number of facilities to be visited could be in the range of hundreds, Acheson said, based on knowledge of what ingredients go to which manufacturer.
"This is going to go on until we feel satisfied we've got it covered. We're not setting the bar at 50 or 100 or 1,000. We're going to keep doing this until we're confident that we've got our arms around it," he said.
Protein concentrates are used in a number of food products such as baked goods.
The announcement came as pet food manufacturer Menu Foods expanded its recall because of possible cross-contamination between melamine-tainted products and other foods made in the same period.
Another company, SmartPak Canine of Plymouth, Mass., issued a recall for all lots of its Live- Smart Adult Lamb and Brown Rice food, which it said had tested positive for the presence of melamine. The food is shipped directly to about 220 consumers and is not available on store shelves, the company said in a statement.
More than 100 brands of pet food have been recalled since March 16 because they were contaminated with melamine.
An unknown number of dogs and cats have been sickened or died after eating chemical-laced pet food. The expansion includes cuts and gravy pet food, as well as other products that were not made with the contaminated wheat gluten supplied by ChemNutra Inc., but were manufactured during the period the chemical-laced gluten was used. While Acheson said he remains confident that none of the products contaminated with melamine ended up as an ingredient in human food, he noted that some poultry and hogs ate feed including some of the recalled pet food. That isn't expected to pose a hazard to humans because of the dilution factor, he explained. Pets that became sickened or died ingested larger dose of melamine because pet food makes up their entire diet. On the other hand, the contaminated pet food made up only a small part of the hog and poultry feed, meaning they got a lesser amount and none of those animals became ill. In addition, pork and poultry make up only a part of the human diet so the amount anyone might eat would be very small. Kenneth Peterson of the Agriculture Department's Food Safety and Inspection Service said some meat and poultry made it to the market and "there is just no evidence of any harm to humans from that chicken or that pork." Animals on farms where the pet food is known to have been used are now being barred from slaughter, he added. The FDA has inspectors in China working with local officials to trace the sources of the contamination, he said. The New York Times, meanwhile, reported that Mao Lijun, the manager of the Chinese firm that supplied the wheat gluten, was detained by Chinese authorities.