TUESDAY, May 1 (HealthDay News) -- Up to 3 million broiler chickens were fed melamine-tainted pet food and then sold on the U.S. market beginning in early February, U.S. health officials said in a press conference held late Tuesday.

The contaminated pet product made its way into poultry feed at 38 Indiana farms, 30 of which produced broiler chickens destined for restaurants and supermarkets, said officials at the U.S. Food and Drug Administration and the U.S. Department of Agriculture.

Approximately 2.5 million to 3 million chickens fed contaminated pet food have already been sold, Kenneth Peterson, assistant administrator for field operations at the USDA's Food Safety and Inspection Service, said during the teleconference. "That's out of a total of 9 billion broilers processed in the U.S. each year," he noted.

Experts from both agencies downplayed any potential threat to human health.

"We still have no evidence of harm to humans or to swine" from the use of the tainted pet product, said Dr. David Acheson, who began his tenure as the FDA's new assistant commissioner for food protection on Tuesday. Acheson said that the contaminated food constituted only about 5 percent of the total feed at the farms. "The risk to humans is small," he said.

Peterson added that some 100,000 breeder chickens are being held in quarantine at some of the Indiana farms. Those chickens have been quarantined and may be euthanized, the FDA and USDA said. The agencies also warned in a statement issued late Monday that "as the investigation continues, additional farms will likely be identified that received contaminated feed."

The announcement comes on the heels of similar discoveries at hog farms across the United States. The USDA first announced on Thursday that meat from 345 hogs suspected of eating the contaminated feed had entered the U.S. food supply. Some 6,000 hogs suspected of eating the contaminated product have since been quarantined and meat from these animals will be withheld from the food supply, both agencies said.

"As with exposure from hogs fed contaminated pet food and for similar reasons related to the dilution of the contamination, FDA and USDA believe the likelihood of illness after eating chicken fed the contaminated product is very low," the agencies said Monday night. "Because there is no evidence of harm to humans associated with consumption of chicken fed the contaminated product, no recall of poultry products processed from these animals is being issued."

In a similar vein, U.S. health officials have continued to reassure American consumers that pork products from hogs fed contaminated pet food were safe, even as reports surfaced that China has routinely added the contaminant melamine to its exported animal food supplements.

In a joint statement issued late Saturday, the FDA and USDA stressed that, "We are not aware of any human illness that has occurred from exposure to melamine or its byproducts." They added that they have also identified no illnesses in swine fed the salvage food tainted by melamine, which was imported from China as an additive to wheat gluten used in dog and cat food.

Melamine, a derivative of coal, is at the center of the United States' largest pet food recall, involving more than 60 million packages of 100 name-brand products. The chemical has been linked to the deaths of at least 16 pets and the illness of possibly thousands of animals.

In the Saturday statement, the FDA and the USDA said the possibility of human illness from eating swine exposed to melamine remains low for several reasons: "First, it is a partial ingredient in the pet food; second, it is only part of the total feed given to the hogs; third, it is not known to accumulate in the hogs, and the hogs excrete melamine in their urine; fourth, even if present in pork, pork is only a small part of the average American diet."

On April 25, the Pet Food Institute (PFI), which represents U.S. pet food manufacturers, asked the U. S. Trade Representative Susan C. Schwab and the Commissioner of the Food and Drug Administration Andrew von Eschenbach for "swift action to answer questions about how melamine, a substance foreign to pet food, ended up in specific ingredients from China," according to a PFI statement.

On Monday, The New York Times reported that Chinese producers routinely add melamine to wheat gluten and rice protein in animal feed products to falsely inflate levels of protein.

In interviews with agricultural workers and managers in China, the newspaper reported that animal feed producers have secretly added melamine to their feed for years because, during tests, it appears to be a protein, even though it doesn't add any nutritional benefits.

"Many companies buy melamine scrap to make animal feed, such as fish feed," Ji Denghui, general manager of the Fujian Sanming Dinghui Chemical Company, which sells melamine, told the Times. "I don't know if there's a regulation on it. Probably not. No law or regulation says 'don't do it,' so everyone's doing it. The laws in China are like that, aren't they? If there's no accident, there won't be any regulation."

"We don't know if this has been going on in China for a long time," Acheson said during a teleconference Monday. "But I have read reports that this is something that has not started recently," he said.

On Thursday, China banned melamine from its food products, but rejected the charge that the substance caused the U.S. pet deaths, the Associated Press reported.

It's not clear how -- or even if -- melamine became fatal in pet food, because it's not believed to be particularly toxic. But U.S. law bans its presence in any form of food, the newspaper said.

The rice protein was imported to the United States by Wilbur-Ellis, an agricultural product importer and distributor. The FDA said it is continuing its investigation of the source of the adulterated pet food, including "tracing products distributed since August 2006 by Wilbur-Ellis throughout the distribution chain."

In their latest statement, the FDA and the USDA said that, as of April 26, they had identified sites in six states where contaminated pet food was received and used in feed given to hogs: California, Kansas, New York, North Carolina, South Carolina and Utah.

On Friday, FDA officials searched the facilities of a pet food manufacturer and one of its suppliers in the continuing probe of the contamination, the Associated Press reported.

The officials searched an Emporia, Kan., pet food plant operated by Menu Foods and the Las Vegas offices of ChemNutra Inc., the news service said, citing information supplied by the companies.

Menu Foods made many of the major brands of dog and cat foods that were recalled because of the melamine-contaminated wheat gluten. ChemNutra supplied Menu Foods with the wheat gluten, which was also imported from China but reportedly from a different supplier than the rice protein.

Both companies said they were cooperating with the investigation, the AP said.

More information

For more information on pet food, visit the U.S. Food and Drug Administration.

SOURCES: May 1, 2007, teleconference with David Acheson, M.D., assistant commissioner for food protection, U.S. Food and Drug Administration; Kenneth Peterson, assistant administrator for field operations, Food Safety and Inspection Service, U.S. Department of Agriculture; Pet Food Institute (PFI) press release; The New York Times; Associated Press

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