As many as 20 million chickens raised for human consumption in several states have been put hold Friday following reports by three federal agencies that their feed was mixed with pet food containing an industrial chemical.

Three government agencies ,namely the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA), are expected to release an assessment report Monday that would determine the possible risks the chickens would pose to human health if eaten.

The 20 million chickens that have been withheld represent a small portion of the 9 billion chickens raised each year in the United States, and the USDA says it will withhold its approval of the suspected chickens until an answer is found.

It is still not clear how many chicken producers have been affected by the hold but federal officials suspect many farms in several states to be involved. As of Friday, no melamine had been detected in the feed used by larger manufacturers but since the investigators know some of the tainted pet food was used in that feed, they placed a hold on the birds.

The announcement follows last week's reports that 38 of the chicken facilities in Indiana had given contaminated feed to poultry raised for human consumption, and that 2.5 to 3 million people ate them.