The Maine Center for Disease Control and Prevention says the strain of E. coli that sickened two children in October, killing one, can’t be linked to the Oxford County Fair.

State health officials sent samples to the U.S. Centers for Disease Control and Prevention. Those tests came back inconclusive.

“While we know the two children were infected by the same molecular strain of Shiga toxin-producing E. coli, or STEC, that same strain was not found in any of the samples that we tested here in Maine, or in the samples we sent to the U.S. CDC,” Maine’s state epidemiologist Dr. Siiri Bennett, said.

Bennett said the majority of E. coli cases that are investigated end with an undetermined cause.

The families of the two children thought they contracted the illness from the petting zoo at the fair.

Twenty-month-old Colton Guay of Poland died of E.coli. Seventeen-month-old Myles Herschaft of Auburn recovered after treatment at Maine Medical Center.

Officials said four samples collected from the Oxford County Fairgrounds tested negative for E. coli at a state lab, and one sample from animal pens tested positive for the presence of STEC. The Maine CDC said lab tests from the U.S. CDC confirmed that the sample that tested positive for the presence of STEC did not match the strain that caused the children’s illness.