The US Justice Department's consumer protection unit has been investigating a norovirus outbreak at a Chipotle restaurant in California. This has indicated that a recent probe launched by federal prosecutors in California has been grabbing a lot of attention at Washington headquarters.

In the wake of a series of foodborne illnesses, Chipotle Mexican Grill has been under a lot of scrutiny. All this has resulted into a decline in Chipotle’s shares and a fall in its fourth-quarter same-store sales.

On Wednesday, Chipotle revealed that the US Attorney's Office for the Central District of California had served it with a grand jury subpoena in December under a criminal investigation carried out by that office and the Food and Drug Administration.

The people familiar with the matter said that the Justice Department's Consumer Protection Branch’s officials contacted Los Angeles federal prosecutors to talk about the early stage inquiry on Thursday.

Generally officials in the Justice Department's headquarters in Washington work along with regional prosecutors, but their interest in the Chipotle matter has underscored the federal government's strengthened enforcement of food safety laws in the recent years.

One of the famous prosecutions include a 2015 case where in a subsidiary of ConAgra Foods Inc decided to plead guilty and made a payment of $11.2 million linked to the shipment of peanut butter contaminated with salmonella.

The ex-head of the Peanut Corporation of America was given 28 years imprisonment in September for his part in a salmonella outbreak that took nine lives.

As part of the subpoena over the Chipotle outbreak, the company has to provide the documents related to an August 2015 norovirus outbreak that took place at one of its restaurants in Simi Valley, sickening over 200 people.