(Adds details on norovirus, Chipotle's next quarterly report, updates stock price)
July 18 (Reuters) - Chipotle Mexican Grill Inc closed a restaurant in Virginia because of a suspected norovirus outbreak among some diners, sending its shares lower on Tuesday.
Investors are keenly sensitive to food-safety issues at Chipotle, which is still working to recover fully from a string of sales-crushing E. coli, salmonella and norovirus outbreaks in late 2015.
Chipotle's stock was off $17.50 at $374.50 in late-afternoon trading on Tuesday after falling as low as $362.51. The shares were trading at nearly $750 before the company's previous food-safety incidents, which battered the chain's profits and reputation.
Chipotle spokesman Chris Arnold said on Tuesday the reported symptoms were consistent with norovirus, a highly contagious virus that can cause severe vomiting and diarrhea.
"We plan to reopen the restaurant today," Arnold said.
The suspected illnesses were first reported by Business Insider earlier on Tuesday. It cited information from iwaspoisoned.com, a website on which consumers document what they believe are incidents of foodborne illness.
"In total, eight reports were made to the website, indicating that at least 13 customers fell sick after eating there from July 14-15," the news site said.
Chipotle voluntarily closed the restaurant on Monday, said Victor Avitto, environmental health supervisor for the Loudoun County Public Health Department, which has jurisdiction over the restaurant on Tripleseven Road in Sterling.
Test results are expected later this week, Avitto said.
Norovirus, known as the "winter vomiting bug," is the leading cause of illness and outbreaks from contaminated food in the United States, according to the Centers for Disease Control and Prevention. It can spread from person to person, as well as through food prepared by an infected person. It often hits closed environments such as daycare centers, schools and cruise ships. Most outbreaks happen from November to April in the United States.
Chipotle will report second-quarter results on July 25. (Reporting by Lisa Baertlein in Boston; Editing by Matthew Lewis and Peter Cooney)