Shares of Chipotle Mexican Grill Inc. fell as much as 3.3 percent after a report that public health officials are investigating a possible illness outbreak in one of the company's restaurants in Los Angeles.

An email from the Los Angeles Health Department's Acute Communicable Disease Control unit says the agency "is aware of reports of illness and is investigating" according to the Business Insider report.

Chipotle said the company is aware of a few online reports, but there is no clinical validation associated with them. The company also said it has not been contacted by customers directly to substantiate these claims.

At least three reports from customers on iwaspoisoned.com say they suffered from vomiting and diarrhea after eating at a Chipotle restaurant located at 4550 W. Pico Blvd. in Los Angeles. However none of the customers said they visited a doctor.