A federal grand jury has indicted four officials at a Northern California slaughterhouse at the center of a massive beef recall, alleging they slaughtered cows with cancer while inspectors were on their lunch breaks and distributed the diseased cattle, prosecutors announced Monday.

MORE: Read the full indictment | Information on indictment [PDF]

Petaluma-based Rancho Feeding Corp. halted operations in February after a series of recalls, including one for 8.7 million pounds of beef. The meat was sold at Walmart and other national chains and used in products, including Hot Pockets.



The U.S. Department of Agriculture has said Rancho processed diseased and unhealthy animals and circumvented federal inspection rules.

The maximum penalty if they're convicted is five years for distribution of the tainted meat and 20 years for sending out fraudulent invoices to try and cover it up.

NBC Bay Area's Mark Matthews contributed to this story.