The crash happened at Route 59 and Higgins Road just before 10 a.m., officials said.
Illinois State Police said the trooper was helping officers with traffic control while they investigated a crash. The trooper put on his emergency lights, but another car hit his squad car.
The occupants in the other car are also hurt in the collision.
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All are expected to be okay, including the trooper, ISP said.
No further information was immediately available.