A Nissan sedan and a Chevrolet SUV crashed head-on at Route 47 and Vanderkarr Road just before 9:30 p.m. in Hebron, McHenry County Sheriff's Office officials said.
Investigators said people were trapped inside their cars after the crash.
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One person needed to be flown to a Rockford hospital in serious condition, officials said. The rest were taken via ambulance to nearby hospitals; their conditions were not immediately known.
The McHenry County Sheriff's Office continues to investigate why the crash occurred.