Chief Steve Millar is on leave due to an ongoing Illinois State Police investigation.
The village said it's "financial in nature," and is related to Millar's role as police chief. Village officials learned of the investigation in May.
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Further details of the investigation have not been made public.
Millar has been in charge of the department for the past five years.
Campton Hills police Sgt. James Levand has been named interim police chief. He has been with the department for the last eight years.