MIAMI (CBSMiami) –The Coast Guard search for a man who fell off a plane is done for the night.

Exactly what happened to the male passenger in a small plane remains a mystery.

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At around 1:30 p.m., the FAA said the pilot of the plane called air traffic control to report someone fell out of the plane about 8 miles south of Tamiami airport.

Radio transmissions found on record the pilot saying, “Mayday, mayday, mayday. I have a door ajar and I’m heading to Tamiami.”

The air traffic controller asked, “You have a door open. Is that what you’re saying?”

“I have a door ajar and a passenger that fell down,” answered the pilot who later added, “He opened the back door and he just fell down the plane.”

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Miami-Dade police confirmed Thursday, that the passenger was a male. They are not releasing any names, but said this is now an official death investigation.

“It’s reasonable, anybody that falls from an aircraft without a parachute  turns into a recovery effort and not a search and rescue,” explained Lt. John Jenkins with Miami-Dade POlice

A search for the missing person began immediately. Helicopters were in the air and boats in the water. Miami-Dade police, fire rescue, and the coast guard scoured the area off the shores of Key Biscayne looking for the missing passenger.

According to the 911 incident report, the plane was about 2,000 ft. above the ocean.

The pilot of the plane returned to Tamiami airport where police arrived to investigate.  “At this time the pilot is very cooperative with the investigation, he’s been talking to them all afternoon,” said Jenkins.

According to the FAA, the plane is a Piper PA 46 aircraft.  That’s a multi-seat plane  that aviation experts told CBS4’s Maggie Newland, can hold up to six people.

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It’s unclear how someone could have fallen out of the plane in midair, or what might have happened, but police are working to figure that out.