Follow CBSMIAMI.COM: Facebook | Twitter

NEW YORK (CBSMiami/AP) — Chipotle temporarily closed a restaurant in a Washington, D.C. suburb after reports a customer became ill, sending shares plummeting more than six percent as the chain works to recover from past food scares.

READ MORE: Juvenile Green Sea Turtle Released In Florida Keys To Join Tour de Turtles Online Race

The company says it shut down a location in Sterling, Virginia, on Monday after becoming aware of a “small number” of reported illnesses. It plans to reopen the restaurant Tuesday after a “complete sanitization.”

Chipotle Mexican Grill Inc. says it is working with health authorities to understand the cause, but the reported symptoms are consistent with norovirus. That can cause nausea, stomach pain and diarrhea. The company notes that norovirus does not come from its food supply and it is safe to eat at its restaurants.

Its shares nonetheless fell 6.4 percent Tuesday to $366.86, after Business Insider reported the closure. Given its history, Chipotle has said in the past any food safety incidents could have an outsized negative impact on its sales, even if the incidents might be considered minor elsewhere.

READ MORE: Cinderella's Castle Gets Makeover Ahead Of Disney's 50th Anniversary Celebrations

Chipotle has been working to bounce back from the food scares that included an E. coli outbreak in the fall of 2015 and a norovirus case in Boston later that year. It’s made tweaks to cooking methods and added training for employees, among other stepped-up safety measures.

In addition, Denver-based Chipotle had been giving away coupons for free burritos and spending more on marketing. Sales had been showing improvement against a low bar of comparison. For the first three months of this year, sales were up 18 percent at established locations. That followed a 20 percent decline for all of 2016.

Despite its efforts to improve its safety procedures, Chipotle has also said it may still be at higher risk for food-borne illnesses than some competitors because of its greater use of fresh produce and meats.

MORE NEWS: 'It Means Absolutely Everything': Family Of Miami's Eddy Alvarez Watch Proudly As He Carries American Flag At Olympics Opening Ceremony

Norovirus is the leading cause of illness and outbreaks from contaminated food in the United States, according to the Centers for Disease Control and Prevention. Infected employees are frequently the source of the outbreaks, the CDC says, often by touching foods such as raw fruits and vegetables with their bare hands before serving them.