State health officials said Friday that at least 15 people, 11 of them children, who visited central Florida festivals have since tested positive for a dangerous strain of E. coli (search) or a potentially fatal kidney disease caused by the bacterium.

While local health officials have said the cases appeared to be linked to petting zoos at the festivals, state Health Secretary John Agwunobi (search) cautioned that the apparent outbreak hasn't been definitively linked to touching animals.

The bacterium also could have been contracted from eating tainted food or from some other activity, Agwunobi said.

The 15 people being monitored by the state Health Department all visited either the Central Florida Fair (search) in Orlando or the Florida Strawberry Festival (search) in Plant City. All have had diarrhea and have either tested positive for the particular E. coli strain or developed the kidney disease, known as hemolytic uremic syndrome, or HUS.

Twelve of the children were confirmed by hospital officials to be in Orlando hospitals Friday, at least three in critical condition. One adult was also hospitalized in Orlando.