Chipotle has been under scrutiny since October when the first of a series of food borne illnesses were linked to several of its restaurants throughout the country.
The lawsuit seeks damages on behalf of investors who bought shares from February 2015 to January 2016.
Chipotle’s latest nightmare began during October and November when an E. coli outbreak affected more than 50 people in nine states.
Since then, sales have been dropping.
This week, shares fell to their lowest point in two years. The chain has faced a 35 percent drop since October.
The company also has been served a subpoena regarding a federal criminal probe linked to Norovirus cases in California last year.