Stefan Ramin, 40, from Hamburg, disappeared last month after reaching the remote tropical island of Nuku Hiva in French Polynesia.
After a week of searches, charred human remains and clothes have been found near a campfire in a remote valley on the island, raising fears that he may have been attacked and eaten by cannibals.
Testing in Paris will conclude whether the ashes belong to Mr Ramin, but is expected to take several weeks.
A squad of 22 police officers on the island are now searching for Henri Haiti, a local guide who took Mr Ramin on a goat hunting trip in the mountains of Nuku Hiva and is believed to be the last person to see him alive.
After setting off on the hunt, Mr Haiti returned to tell Ms Ramin’s girlfriend Heike Dorsch, 37, that there had been an accident and that Mr Ramin had been injured. But when she tried to raise the alarm, Mr Haiti allegedly attacked her and tied her to a tree, before fleeing the scene.
Miss Dorsch managed to escape after several hours and alert authorities. The army has since joined in the hunt for Mr Haiti.
Mr Ramin set off with Miss Dorsch from Germany in 2008 on what was supposed to be the trip of a lifetime. They arrived on Nuku Hiva, largest of the Marquesas islands, in their catamaran on Sept 16. They has planned to spend several months in French Polynesia.
Mr Ramin, who lists “travelling, blue water sailing, kiting, kitesurfing, surfing, diving” as his interests on Facebook, had been missing for a week when the police found his remains. Bones, teeth and melted fillings were also found in the campfire ashes.
Investigators believe a “human body was hacked to pieces and burned”, according to the Daily Mail.
A spokesman for the German foreign ministry said it was “aware of the case and in contact with locals authorities.”
News websites in French Polynesia said the incident had shocked the nation.
“No one can believe what has happened,” Deborah Kimitete, the deputy mayor of Nuku Hiva, told the local news website Les Nouvelles.
“This has never happened here before, this is the first time, it’s horrible.”
Les Nouvelles also reported that Mr Haiti’s family had been out looking for him. He was described by one local as young man who loved sport and was well known in the village.
Nuku Hiva has a population of just over 2000 and has a history of cannibalism, but the practice was believed to have ceased. The island featured in the stories of Herman Melville, author of Moby Dick.