A west suburban man found floating in Lake Michigan near Montrose Beach on the North Side on Sunday drowned, an autopsy has shown.

Friends found Raymundo Zambrano unresponsive in the water about 2 p.m. near the 4400 block of North Lake Shore Drive, according to Chicago Police and the Cook County medical examiner’s office.

The 49-year-old West Chicago resident was taken to Weiss Memorial Hospital, where he died at 3:09 p.m., the medical examiner’s office said. An autopsy Monday showed he drowned, and ruled his death an accident.

Area North detectives are investigating.