State health officials said this afternoon that two toddlers who fell ill with an E. coli infection had the same strain of the dangerous bacteria.

“The strain and molecular typing from each patient was identical, making it highly likely that the cases acquired the illness from same source,” said Dr. Siiri Bennett, the state epidemiologist for the Maine Center for Disease Control and Prevention. “We cannot say with certainty what that common exposure might have been.”

The strain, known as O111, is one of many strains that can be responsible for an illness” such hemolytic uremic syndrome, or HUS, a particular strain of E. coli.

One of the toddlers, 20-month-old Colton James-Brian Guay, died this week, while another, Myles Herschaft, remained in fair condition this afternoon at Maine Medical Center. Myles, 17 months, of Auburn, also suffered from hemolytic uremic syndrome.

The state is still investigating the source of the E. coli infection, although the families of the toddlers have publicly said that they both visited the petting zoo at the Oxford County Fair in late September.