The culprit that made hundreds of people sick after eating at a Chipotle store in Powell late last month is Clostridium perfringens.

Though food samples from the store tested negative for the bacteria, the Delaware General Health District reported Thursday morning that stool samples collected from sickened customers sent to the U.S. Centers for Disease Control contained the toxin that Clostridium perfringens produces.

The bacteria can infect food that is not kept at a safe temperature. The store had been cited by health officials just prior to the outbreak for food not being kept at proper temperatures. The exact source of the bacteria is not yet known, and samples of food are still being tested by the CDC.

The health district identified 647 people who self-reported becoming sick after eating at the store, located at 9733 Sawmill Parkway, between July 26 and July 30.

The Columbus Dispatch has the story.