The Los Angeles Times said Sunday that since the Hallmark Meat Packing was accused of creating beef products from so-called downer cattle, school officials across southern California have been trying to determine if they had purchased any contaminated meat.

"We're in contact with our suppliers, and they're in contact with their suppliers. It's a huge chain of activity," San Diego Unified School District official Joanne Tucker said of the ongoing safety effort.

As a precaution, the California Department of Education has asked all area schools not to serve any items containing ground beef until a thorough investigation can be completed.

The Times said the U.S. Department of Agriculture is heading up the inquiry into the slaughterhouse in Chino, Calif., where cattle too weak to walk were used for food products.

Under USDA regulations, using "non-ambulatory" cattle for products destined for human consumption is illegal due to concerns of spreading bovine spongiform encephalopathy, commonly known as mad cow disease.