The Delaware County District of Health says unsafe food temperatures were behind an illness outbreak at the Sawmill Parkway Chipotle earlier this month.
The district found evidence of a pathogen called Clostridium perfringens in stool samples from the Centers of Disease Control and Prevention.
Delaware County Health Commissioner Sheila Hiddleson says they don't know which food in particular caused the illness.
"If you think about how this particular restaurant serves food, and many of us have eaten there, they kinda join all those foods together either in a burrito or in a bowl, so we may never know exactly what food caused this," Hiddleson said.
The health district will continue to examine data and have sent additional food samples to the CDC for testing.
Nearly 650 people reported symptoms like diarrhea and nausea after eating at the Sawmill Parkway Chipotle. At least two have filed lawsuits.
The company had closed the store for a day of cleaning when it became aware of reported illnesses.
Chipotle CEO Brian Niccol has said Chipotle will be retraining employees across the country on food safety.
The Associated Press contributed to this report.