BOSTON (Reuters) – Chipotle Mexican Grill Inc said it will reopen a Virginia restaurant on Wednesday, two days after it was closed due to reports that several customers had fallen ill with suspected norovirus.

Shares of the restaurant chain tumbled more than 4 percent on Tuesday after Chipotle reported the closure. The former high-flying chain is still fighting to repair its reputation and resuscitate its sales after a string of high-profile food safety lapses in late 2015.

Chipotle voluntarily closed the restaurant in Sterling, Virginia, on Monday, according to a health official for the Loudoun County Public Health Department, which has jurisdiction over the restaurant, about 30 miles (48 km) northwest of Washington.

About 13 people became sick last week, according to a website that follows incidents of foodborne illness. Test results are still pending.

Chipotle stock, which traded well above $700 prior to 2015 reports linking the chain to outbreaks of E. coli, salmonella and norovirus, was off 1.4 percent at $369.56 on Wednesday.

“It is unfortunate that anyone became ill after visiting our restaurant, and when we learned of this issue, we took aggressive action to correct the problem and protect our customers,” Chipotle Chief Executive Officer Steve Ells said in a statement.

“While the restaurant was closed, multiple teams performed complete sanitization of all surfaces,” Ells said.

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.

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.

(Reporting by Lisa Baertlein in Boston; Editing by Jeffrey Benkoe)