Police say the man approached a home and identified himself as a police officer. He told the person who opened the door that he was there to warn them about burglaries in the area.
Investigators say he was wearing a black shirt and pants and had a police-style utility belt. He left in a dark-colored car with Illinois license plates.
The Zion Police Department said that no officers were in the area at the time.
The department noted that Zion Police officers drive black and white squad cars and that anyone may ask to see a badge and police ID if approached by a plainclothes officer.