The USDA's Food Safety and Inspection Service evaluated plants that supply beef to the National School Lunch Program, among other federal food assistance programs.

The audit comes on the heels of a 143-million-pound beef recall in February after an undercover video at Westland/Hallmark Meat Packing Co. -- a national lunch program supplier -- in Chino, Calif., showed handlers allegedly using abusive methods to make downed cattle walk to slaughter. The tactics violate federal regulations that ban downer cattle slaughter for food to help prevent bovine spongiform encephalopathy and other diseases from entering the food supply.

Requested by Sen. Herb Kohl, chair of the Senate Appropriations agriculture committee, the review issued three separate "noncompliance" violations to facilities for overcrowding and excessive use of force. Operations were temporarily suspended at a fourth facility using insufficient stunning methods; it has since reopened after implementing change. The USDA left all facilities unnamed.

While most of the 18 plants met general humane standards, Kohl expressed concern that at least one had a violation serious enough to warrant suspension. He also noted that the USDA is working to stregthen plant inspection efforts to best ensure violations and mistreatment issues are caught and corrected.