Three of the children did not have to go to the hospital, the release said. But the youngest, a 2-year-old boy, died from complications of the disease at a hospital Monday.
All four children visited animal areas or the petting zoo, which have been closed to the public since the reports, the county said.
Symptoms of E. coli can include stomach cramps, diarrhea and vomiting. Some infections are mild, but others can be life-threatening. People of all ages can be infected, but young children and the elderly are more likely to develop severe symptoms.
The city asked that anyone who had symptoms on or after June 8 report it to a health care provider.
The types of E. coli that can cause illness can be transmitted through contaminated water or food, or through contact with people or animals.