Chipotle Mexican Grill Inc. has been slapped with a subpoena in a federal crime probe concerning the outbreak of norovirus cases at the firm’s restaurants in California in 2015, according to Reuters.

The company, still reeling from the public relations nightmare that such an outbreak can cause, saw its shares fall almost five percent in trading yesterday, bringing the decline in value to about 30 percent since the end of October, when the company had first reported an outbreak of E.coli at some of its stores.

Chipotle announced it had received the subpoena back in December of last year and was part of an investigation by the United States Department of Justice and the Food and Drug Administration, adding a federal grand jury will make a decision as to whether or not or file charges.

The subpoena will require the company to surrender a broad range of documents that are related to the norovirus outbreak at a restaurant in Simi Valley, California, in which over 200 people became ill, including 17 workers at the store.  Two California residents filed suit for damages after they became sick after eating at that location in August of last year.

A spokesman for Chipotle, Chris Arnold, said the subpoena only covers the isolated incident at the Simi Valley location, but declined to discuss any other aspects of the investigation.

This latest development is just another headache for the firm, leading the company to project a 14.6 percent drop in fourth-quarter same-store sales, which if it holds true, would be the first time the business has recorded a quarterly decline since going public in January of 2006,

Since the outbreaks began, the company has had to do a major sanitizing project on all its affected restaurants and send food for testing at government labs, trying to assist public health officials to determine the exact causes of the outbreaks.

Health officials in other states in which Chipotle has experienced food-safety issues say they have not been contacted by the federal agencies.