Toxicology tests have been ordered to determine how a member of the Australian Navy died in Oman, but it is believed his death is linked to dangerous bodybuilding supplements.

The ABC understands the 22-year-old leading seaman was found unconscious in a hotel room by colleagues who tried unsuccessfully to revive him.

"It is with deep regret the Australian Defence Force can confirm the death of a Royal Australian Navy sailor in the Middle East," the Defence Force said in a statement.

"The sailor was deployed on Operation Manitou in HMAS Darwin.

"The ship was in Muscat, Oman on a scheduled port visit and the sailor was on shore leave in the city when he was found unconscious."

It is believed the sailor may have consumed dangerous bodybuilding supplements which had been purchased locally.

Defence has offered its sympathy to the sailor's family and friends but says it will not comment further.

"Defence is providing support to the sailor's shipmates and family and asks that media respect the family's privacy at this difficult time," the statement said.

"The Australian Defence Force Investigative Service is assisting local authorities with investigations."