The Kansas health department is yet to find the cause and source of a gastrointestinal illness that affected at least 10 people who ate at a Buffalo Wild Wings Inc restaurant, a spokeswoman for the department's Johnson County office said.

Shares of the popular chicken wings chain fell as much as 7.8 percent to a 15-month low of $138.31 on Wednesday.

The Johnson County Department of Health and Environment said on Tuesday that it was working with state health officials in probing reports of gastrointestinal illnesses that affected the people, who ate at a Buffalo Wild Wings outlet in Overland Park in suburban Kansas City. (

Laboratory results are awaited, the department said, adding that there were currently no confirmed cases of norovirus.

"We expect (the test results) in the next couple days," said Barbara Mitchell, the public information officer at the department. "This time of year, we typically have norovirus in the area," she said.

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Buffalo Wild Wings voluntarily closed the restaurant on Saturday for cleaning and reopened it on Sunday following consultation with the health department, a spokesman said in an email.

Norovirus is the most common cause of food-borne illnesses and acute gastroenteritis in the United States, with 19 million to 21 million cases and 570-800 deaths annually, according to the U.S. Centers for Disease Control and Prevention.

State health officials said last month that they were probing a norovirus outbreak among customers at the New Theatre Restaurant in Overland Park.

"I don't believe there's anything that is connected (to the New Theatre outbreak) but we don't know that as of yet either," Mitchell said.

The news comes a day after burrito chain Chipotle Mexican Grill Inc said a federal criminal probe linked to a food-safety incident at a California restaurant had widened into a national investigation.

(Reporting by Rodrigo Campos in New York and Ramkumar Iyer in Bengaluru; Editing by Kirti Pandey)