Health officials in Ohio still don’t know the cause of an apparent outbreak at a Chipotle Mexican Grill there that has sickened more than 600 people.
In an update late Tuesday, the Delaware General Health District said that the Ohio Department of Health has sent samples from people who were sickened to the Centers for Disease Control and Prevention for further testing.
Samples of the food are still pending, the district said.
Last week, tests came back negative for salmonella, shigella, E. coli and norovirus.
The district says that 624 people suffered from gastrointestinal symptoms after eating at a Chipotle in suburban Columbus between Thursday, July 26, and Monday, July 30.
Chipotle voluntarily closed the restaurant after the illnesses were reported. The company cleaned and sanitized the restaurant and tossed open food and was given the go-ahead to reopen the location on July 31.
The incident sent the company’s stock price falling, but it has since recovered after the chain reported that it had its strongest summer sales day of all time that Tuesday, thanks to a free guacamole promotion.