Add the U.S. Attorney for the District of Columbia to the list of those probing fast food chain Chipotle over its hiring practices.

Since 2010, The U.S. Immigration and Customs Enforcement agency has been investigating  Chipotle on allegations that it has hired undocumented workers. That investigation has thus far focused on locations in Minnesota (where 450 illegal employees were found and fired), Atlanta, Los Angeles, Virginia and Washington D.C.

On Tuesday, the company disclosed, in a Form 8-K filing with the U.S. Securities and Exchange Commission, that “the office of the U.S. Attorney for the District of Columbia (USAO) informed Chipotle that [it] is conducting an investigation into possible criminal securities law violations relating to our employee work authorization verification compliance and related disclosures and statements.”

“This investigation is in addition to previously-disclosed investigations by the U.S. Department of Homeland Security, including its Immigration and Customs Enforcement arm, as well as the USAO and the SEC, into our compliance with employee work authorization verification requirements and related disclosures and statements,” the company said. “We intend to continue to fully cooperate in the government's investigations.''

In a related filing last week, Chipotle disclosed that, on May  17, it “received a subpoena from the SEC pursuant to a formal order of investigation by that agency requesting that we provide information regarding our compliance with employee work authorization requirements, our related public statements and other disclosures, and related information. “