The crash happened just after 2 p.m. in Spring Grove, McHenry County officials said.
"Spring Grove Police Department was responding to assist another local jurisdiction with a call for service," an update from police read in part. "While responding, the Spring Grove Police Officer was involved in a traffic crash at the intersection of Illinois Route 12 and Spring Grove Road."
At least eight people had injuries, fire department officials said. Four people were taken to a local hospital and one person was flown to a hospital in Rockford.
No further information about the crash was available.