Ricardo Lopez of the LA Times reported today that the U.S. Department of Agriculture’s inspector general has opened an investigation into the Northern California firm behind a massive recall of nearly 9 million pounds of beef products, raising the possibility of criminal wrongdoing by the company.

Rancho Feeding Corp. of Petaluma on Saturday announced a recall of 8.7 million pounds of beef products processed at its plant over the last year and sold in California and three other states. They included whole carcasses, beef tongue, head, tripe and oxtail.

Federal regulators said that the plant “processed diseased and unsound animals” without a full federal inspection. As a result, the agency said, the “products are … unsound, unwholesome or otherwise are unfit for human food and must be removed from commerce.”

The involvement of the USDA’s inspector general signals that there may have been criminal wrongdoing, according to food safety attorney Bill Marler in Seattle.

The USDA is “taking it up a notch,” Marler said. It’s “not very usual” for this to happen, he added.

Though regulators haven’t disclosed many details, Marler said the company could face criminal charges if it knowingly shipped “adulterated” meat products without inspection.

There have been no reported illnesses linked to the beef products in question, the company and the USDA said.

A call seeking comment from Rancho Feeding went unanswered Tuesday.