In the investigation following the March 16 pet food recall that sickened or killed domestic pets across the country, the Agriculture Department and the Food and Drug Administration found that chicken feed in some farms in Indiana contained byproducts from contaminated wheat gluten imported from China.

The contaminated rice protein and wheat gluten, which is believed to be tainted with the industrial chemical melamine, was allegedly distributed to more than 30 poultry farms across Indiana. The federal agencies also cautioned that other farms in states across the United States could have received contaminated feed, but have stopped short of issuing a recall of poultry products processed by the farms.

The FDA and USDA's decision to not issue a recall of poultry products processed by the affected animals was based on the small probability of humans contracting an illness from eating chicken that were fed the contaminated product.

Meanwhile, both federal agencies also declined to issue a recall after determining that hogs in certain states, including California, may have also been fed the melamine-tainted pet food.