The Chicago Fire Department responded to a report of a body in the lake just after 11 a.m.
The body was found near Hollywood Beach, close to Sheridan Road and Ardmore Avenue.
CPD said it was the body of a man between the ages of 30 and 40.
Chicago police will handle the investigation.
This comes after a 6-year-old boy was rescued from Lake Michigan at Montrose Beach Wednesday night. He is in critical condition.
READ ALSO | Boy, 6, hospitalized after being pulled from Lake Michigan at Montrose Beach
Chicago beaches do not officially open until Friday at 11 a.m. Lifeguards will be on-duty daily from 11 a.m. to 7 p.m. through Labor Day.
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This is a developing story. Check back for updates.