Five children sickened by E. coli infections last month drank unpasteurized milk, an investigation has found.

The state Department for Public Health worked with local health departments, hospitals and health care providers to find the cause of the outbreak, which affected children in Hardin, Oldham and Boone counties.

Four of the five children developed hemolytic uremic syndrome.

Dr. Stephanie Mayfield, commissioner of the state health department. “Unpasteurized milk is dangerous and has not undergone a process to kill bacteria before it is consumed …  raw milk, no matter how carefully it is produced, may contain pathogens.”