A 2-year-old has died and three other children were sickened by E. coli after coming into contact with animals at the San Diego County Fair, health officials said Friday.

The San Diego County Health and Human Services Agency (HHSA) released a statement late Friday stating that the source of the E. coli is under investigation, but officials have determined that all of the children sickened with symptoms of E. coli had reported visiting a petting zoo area at the fair.

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"Our sympathies go out to the family of the child that died from this illness," Wilma Wooten, the county's public health officer, said in a statement.

"While most people recover from this illness without complications, 5 to 10 percent of people diagnosed with STEC develop life-threatening kidney infections," she continued.

Four cases of E.coli bacteria linked to San Diego County Fair. pic.twitter.com/0zRZTNgU5l — SD HHSA (@SDCountyHHSA) June 29, 2019

Three other children ages 13 and under were also sickened by the bacteria, according to the HHSA, but they did not require hospitalization. Officials did not release the names of the four children but said they all visited the fair between June 8 and June 15 and began showing symptoms between June 10 and 16.

"Our hearts, our prayers, our thoughts go out to the family and the friends of this young child," Timothy Fennell, CEO of the Del Mar Fairgrounds, said Friday night at a press conference, according to NBC News. "We're devastated."

Fennell added Friday night that the fair's petting zoo would be closed but said the rest of the event's attractions and food stalls would remain open as planned.

"No contamination has to do with food service or food at all. That’s been verified," he said, according to NBC.

A spokesperson for the Del Mar Fairgrounds told NBC that the fair attracts 1.4 million to 1.6 million visitors every year.