• Health officials have discovered the source of a foodborne-illness outbreak that sickened at least 647 people who ate at a Chipotle restaurant in Powell, Ohio.
  • Stool samples taken from customers who got sick after eating at the restaurant tested positive for Clostridium perfringens, a foodborne illness that occurs when food is left at an unsafe temperature, a spokeswoman for the Delaware General Health District said.
  • “Chipotle field leadership will be retraining all restaurant employees nationwide beginning next week on food safety and wellness protocols,” Chipotle CEO Brian Niccol said in response to the outbreak.
  • Chipotle has spent millions of dollars on measures to improve food safety after an E. coli outbreak three years ago affected restaurants in 14 states.

Health officials say they have identified the cause of a foodborne-illness outbreak stemming from a Chipotle restaurant in Powell, Ohio, that sickened at least 647 people.

Stool samples taken from customers who got sick after eating at the restaurant tested positive for Clostridium perfringens, a foodborne illness that occurs when food is left at an unsafe temperature, according to Traci Whittaker, a spokeswoman for the Delaware General Health District.

In response to the outbreak, Chipotle CEO Brian Niccol said: “Chipotle field leadership will be retraining all restaurant employees nationwide beginning next week on food safety and wellness protocols.”

He also said restaurants would be adding a “recurring employee knowledge assessment” to their daily food-safety routines.

"Chipotle has a zero-tolerance policy for any violations of our stringent food-safety standards, and we are committed to doing all we can to ensure it does not happen again," he said. Chipotle shares fell more than 4% Thursday afternoon.

The health department said that no specific food has been identified as the source of the illness and that the Centers for Disease Control and Prevention was conducting food and stool testing.

Business Insider reported last month that Chipotle temporarily closed the restaurant at the center of the outbreak, at 9733 Sawmill Parkway in Powell, on July 30 after receiving reports of customer illnesses. Reported symptoms included vomiting, diarrhea, and stomach pains.

Records show that local health officials inspected the Powell Chipotle on July 26 and found violations related to food not being held at proper temperatures. Specifically, they observed that lettuce was not properly cooled and that beans were not held at a warm enough temperature.

Customers who reported getting ill after eating at the restaurant visited the location between July 26 and July 30, according to the Delaware General Health District. No customers have reported getting sick after eating the restaurant since it reopened.

Health officials have inspected nearby Chipotle restaurants since the illness outbreak and found additional violations.

In two of the restaurants, inspectors found boxes of raw chicken "leaning" on other packaged foods, according to health records. Inspectors also found foods that were not being held at proper temperatures.

Chipotle has spent millions of dollars on measures to improve food safety after an E. coli outbreak three years ago affected restaurants in 14 states.