The man was last seen swimming near the shore at Pratt Beach, 1050 West Pratt Boulevard, in Rogers Park, around 9:50 p.m.
Citing police dispatch reports, the man was floating on his back, one to three buoyes south of the Pratt Beach pier, when he dropped out of sight.
At 10:12 p.m., police were trying to keep onlookers away from the pier while rescue workers searched for the missing swimmer.
Divers were in the water around 10:14 p.m. and officers were combing the area for any unattended articles of clothing.
If more details become available, this article will be updated accordingly.
Photo credit: Keith H.
UPDATE: The search was suspended at 10:57 p.m. Authorities were unable to find anyone in the water.
UPDATE: South of Rogers Park, officials were also looking for a missing man at Montrose Beach, 200 West Montrose Harbor Drive, in Uptown.
The subject, a black male wearing dark shorts and a white shirt, was last walking into Lake Michigan, around 9:40 p.m.
The man's friends frantically searched the area before notifying police, said authorities.
The Chicago Fire Department and the Chicago Police Marine Unit responded to the area, but were able to the find the man.