WASHINGTON, D.C. – The federal government has launched a criminal investigation into an outbreak of foodborne illness linked to one Chipotle Mexican Grill, Reuters reports. The rash of norovirus sicknesses that happened last fall in California and Massachusetts, plus an earlier E. coli outbreak also traced to the fast-casual chain, have sent Chipotle into a tailspin. The chain has reported an estimated 14.6% drop in fourth-quarter, same-store sales.

The U.S. Food and Drug Administration and the Department of Justice have launched a joint investigation into the outbreak at a Simi Valley, California, location. A federal grand jury will determine if official charges will be filed against Chipotle. The government’s involvement is part of an overall strategy to focus on food safety.

Some of those sickened by the outbreaks have filed lawsuits against Chipotle. The company spokesman’s only comment clarified that the subpoena was for the Simi Valley case. Other states have also reported foodborne illnesses related to Chipotle, including Oregon, Washington and New York.

Such outbreaks highlight the need to have fully trained foodservice workers and protocols in place to keep food prep and cooking areas sanitized and clean. NACS offers certification training for foodservice personnel.