The illnesses were first reported in Germantown, southwest of Dayton, after a July 3 customer appreciation picnic for a lawn care business.

A spokesman for the Montgomery County health department says more than a dozen people have been hospitalized. A 4-year-old girl, a 14-year-old boy and a 73-year-old man remained hospitalized Tuesday with complications from the bacteria.

It can cause diarrhea, dehydration and, in severe cases, kidney failure.

Officials trying to determine how the outbreak started are interviewing people who ate at the picnic and later fell ill.