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MIAMI (CBSMiami/AP) - Authorities are investigating the death of a 31-year-old man who had been diving off Key West.

In a statement Wednesday, Monroe County Sheriff's Office spokesman Adam Linhardt said Jonathan Christopher Saporito was diving Tuesday with a hookah rig, which uses a compressor floating on the water's surface to pump air through hoses, instead of using traditional scuba tanks.

Linhardt said a Coast Guard crew found two other men attempting to revive Saporito aboard a private 24-foot boat.

The men told the sheriff's office they had been taking turns diving at a depth of roughly 20 feet (6 meters) for several hours. At 7 p.m., Saporito failed to resurface. He was unresponsive when he was pulled aboard.

An autopsy is scheduled.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)