(CNN) -- Public health officials in North Carolina said Thursday eight cases of E. coli have been confirmed in the state, and 13 possible cases are being investigated in what they believe might be a growing outbreak.
Four of the confirmed cases are children, and three of them are being treated in hospitals for kidney failure -- a typical complication of E. coli, according to Public Information Officer Julie Henry of the North Carolina Health and Human Services.
The first illnesses were reported around October 15, Henry said. State officials believe that most of the victims attended the North Carolina State Fair, which ran from October 13 through October 23 in Raleigh and which drew nearly a million attendees.
But Henry said Thursday that officials do not know the source of the E. coli.
Brian Long, director of the North Carolina State Fair press office, said that fair officials are cooperating with public health officials as they try to determine the source of the outbreak.
"Right now there are still far more questions than answers, and we know the investigation will take time. But we are eager to help investigators any way we can," Long told CNN.
"We are keeping the patients and their families in our prayers, and hoping they recover fully and quickly," said Long.
Lab test results are expected early next week to help health officials determine whether all the cases have the same genetic fingerprint of E. coli.
"We want to make people overly aware that this is still the incubation period, so people can be getting sick," Henry said.
Some common symptoms of E. coli include cramping, fever, nausea and diarrhea.
Officials have alerted hospitals, physicians and county health departments to be on the lookout for patients with possible E. coli symptoms.