THE remains of the unknown sailor believed to be the sole survivor of Australia's most enduring wartime mystery -- the sinking of HMAS Sydney off Western Australia -- have been unearthed on Christmas Island in the Indian Ocean. The Defence Department last night confirmed that bones had been discovered in the island's Old European Cemetery by a navy-led team of experts and, once removed, would be taken to Sydney for further forensic tests in an attempt to establish identity.

The discovery is yet another piece to a puzzle that has fascinated and frustrated historians for more than half a century. The find is the only known link to the Sydney, last seen off Shark Bay, before it was believed to have been sunk on November 19, 1941, by the German raider Kormoran.

All 645 men on board perished, making it the biggest maritime disaster in the nation's history.

But it now seems that at least one sailor may have managed to escape the disaster, only to die on a life raft that eventually washed up on Christmas Island, 2600km northwest of Perth, three months later.

The Royal Australian Navy at the time denied that the mystery man was from the Sydney, despite clothing consistent with navy uniform being found on the body.

A doctor examined the remains and the sailor was buried with full military honours.

But many relatives of those who perished on the light cruiser, desperate for the mystery to be solved, refused to accept the initial denial.

A parliamentary inquiry in 1999 -- nearly 60 years after the event -- found it was highly probable the unknown sailor was a Sydney crewman.

A navy expedition team found the remains very close to the position identified by witnesses to the original burial.

That position was corroborated by separate photographs taken in 1950.

''We are excavating remains in an unmarked grave that may be those of the unknown sailor from the HMAS Sydney,'' expedition leader Captain Jim Parsons said last night.

''Further work will need to be done to establish the characteristics of the skeleton before we can be fully confident.''

The team -- which includes an archeologist, a forensic anthropologist and two forensic odontologists -- have still to remove the remains from the grave.

''The process is long and painstaking, as the complete skeleton has to be exposed and recorded, and all the dirt removed before any bones are removed,'' Captain Parsons said.

''Even then, each bone must be carefully lifted to avoid breakages.

''Subsequent skeletal and dental analysis will be taken to Sydney to possibly identify the remains.''

The remains are expected to be taken to the University of Sydney where forensic pathologists will attempt to establish an identity with dental records and an attempt will be made to recover DNA.

But Captain Parsons said the likelihood of a positive identification was low; only half of the crew's medical and dental records were available.

''All records current at the time were lost with the ship,'' he said.