Chipotle Mexican Grill Inc. (CMG) could be in hot water once again. 

Shares of the restaurant chain dropped 4.37% to $299.47 late Wednesday, Dec. 20, on heavy trading volume after reports surfaced of a food-related illness possibly contracted at a Chipotle location in Los Angeles. 

Users on the site IWasPoisoned.com, which serves as a platform for diners to anonymously report suspected foodborne illnesses, said they experienced symptoms including vomiting, diarrhea and nausea after eating at the Chipotle restaurant located on Pico Boulevard in L.A.

"We are aware of some employees who have been ill, and those employees are being held out of work, as is our policy if employees are sick," a Chipotle spokesperson told TheStreet via email. "We reported those illnesses to local health officials (also a policy) who inspected that restaurant yesterday and were pleased with our operations, and the restaurant remains open for business."

On IWasPoisoned, five reports were made in total, detailing seven people who became ill after eating at the Pico location around Dec. 13. 

"We take any report of illness very seriously. We are aware of a few reports (two of which appear to be the same) on user generated reporting sites but there is no clinical validation associated with those reports, and we have not been contacted by customers directly to substantiate these claims," Chipotle said.

"We have also not been made aware of any illness reports made to local health officials. As a precautionary measure, we have implemented heightened preventative procedures at this restaurant, which we do as a matter of policy if we ever receive reports of illness (even if they are not substantiated)."

A similar outbreak occurred in July, when a string of foodborne norovirus tied to a Sterling, Virginia, location led to the temporary closure of the restaurant. Chipotle shares fell more than 7% on the news. 

About two years ago, E. Coli broke out in Chipotle restaurants in 14 states. 

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