Four cases of a toxin producing the bacteria and one case of a resultant blood syndrome stemmed from customers eating at the Portillo’s at 235 E. North Ave. in Glendale Heights on July 16 and 17, IDPH wrote in a health alert.

The “possible issue” came from four customers during that time period, Portillo’s spokeswoman Sara Wirth wrote in a Saturday statement. She said the company reexamined its food safety protocols after learning of the outbreak.

“Across Portillo’s, we have extensive sanitary and food handling guidelines in place, including daily deep cleanings of all restaurants,” Wirth said. “Once notified, we moved quickly and began assisting with the investigation and revisiting our food safety best practices with our team members to mitigate potential future risk.”

The health department is urging doctors to consider an E. coli diagnosis in symptomatic patients who have recently eaten at the location.

With an average incubation period of one to 10 days, the condition can include cramps and diarrhea and, in children and older adults, kidney failure and red blood cell destruction, IDPH said.