Health officials in San Diego County, California say a 2-year-old boy died last week due to an E. coli infection.
Three other children, ages 9 to 13, have also been sickened by the bacteria.
Officials say all four visited the San Diego County Fair between June 8 and June 15, and all of them visited animal exhibits, a petting zoo or had other contact with livestock at the fair.
“Although no specific animal activity has been implicated at this time, out of an abundance of caution, the petting zoo has been closed and public exposure to animals has been restricted until the fair closes,” announced San Diego County Health Officer Dr. Wilma Wooten.
The boy who died got sick on June 19, four days after visiting the fair.
Health inspectors are trying to determine the source of the bacteria but say all food stands at the fair have been inspected and found to be safe.