Three of the children did not have to go to the hospital, the publication said. But the youngest, a 2-year-old boy, died of disease complications in a hospital on Monday.
All four children visited animal areas or the petting zoo that has been closed to the public since the reports, the county said.
Symptoms of E. coli may include stomach cramps, diarrhea and vomiting. Some infections are mild, but others can be life-threatening. People of all ages can be infected, but toddlers and the elderly are more likely to develop serious symptoms.
The city requested that anyone who had symptoms on June 8 or later reported it to a health care.
The types of E. coli that can cause disease can be transmitted via contaminated water or food or by contact with humans or animals.