Chipotle temporarily closed one of its restaurants in Sterling, Virginia, after an unspecified amount of customers reported illnesses with symptoms consistent with norovirus after eating food at the Mexican grill, The Associated Press reported.

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According to the AP a “small number” of customers reported the illnesses.

Chipotle said the company planned to reopen the Virginia location the same day after completing a full sanitation of the restaurant.

Chipotle officials are working with health officials to discover the cause of the illnesses. Restaurant officials assured customers that norovirus does not come from its food supply.

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Chipotle's shares dropped more than six percent Tuesday as investors responded to the incident with concern.

Symptoms of norovirus include nausea, vomiting, stomach pain and diarrhea.

In 2015, Chipotle's revenue and reputation suffered after an E. coli outbreak at restaurants in nine states and a norovirus outbreak at a Boston location. Approximately 500 customers reported illnesses.

"We may be at a higher risk for food-borne illness outbreaks than some competitors due to our use of fresh produce and meats, rather than frozen, and our reliance on employees cooking with traditional methods rather than automation," Chipotle officials said at the time.

According to the Centers for Disease Control and Prevention, restaurant workers are often the source of norovirus outbreaks, as they often touch foods such as raw fruits and vegetables with their bare hands before serving them.

In 2016, Chipotle shut down all locations for a day retrain employees on food safety.

MIAMI, FL - APRIL 27:  Chipotle restaurant workers fill orders for customers on the day that the company announced it will only use non-GMO ingredients in its food on April 27, 2015 in Miami, Florida.  The company announced, that the Denver-based chain would not use the GMO's, which is an organism whose genome has been altered via genetic engineering in the food served at Chipotle Mexican Grills.  (Photo by Joe Raedle/Getty Images)

Credit: Joe Raedle

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Credit: Joe Raedle