Chipotle reopened a restaurant in Virginia on Wednesday that was temporarily closed after customers reported getting sick with suspected norovirus.

"While the restaurant was closed, multiple teams performed complete sanitizations of all surfaces," Chipotle Mexican Grill CEO Steve Ells said in a statement. "We also provided support to any customers or employees who had reported illness to ensure their well-being."

Chipotle (CMG) shuttered the restaurant a day earlier for a deep cleaning after customers fell ill with symptoms "consistent with Norovirus," the statement said. The company added the illnesses were isolated to the location in Sterling, a suburb of Washington, D.C. Norovirus is highly contagious and can be "introduced by people into any closed environment," the statement said.

"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," said Ells.

The Health Department of Loudoun County, where Sterling is located, said it was still trying to identify the type of illness that caused Chipotle customers to complain of nausea, vomiting and diarrhea over the last two days. But it didn't immediately return a message asking how many people got sick.

The company's stock dropped 4% on Tuesday. On Wednesday it had rebounded slightly but was still trading lower at midday.

Food safety concerns have vexed Chipotle in the past.

The company was hit by multiple outbreaks of E. coli and norovirus starting in 2015, sickening hundreds of customers across about a dozen states and dragging down sales. It temporarily closed restaurants to fix the problem and suffered its first quarterly loss last year.

This prompted Chipotle to close all 1,900 of its restaurants for a four-hour food safety session in 2016.