Detectives are sifting through missing persons files across Australia after the grisly discovery of a man's head by a holidaymaker on Rottnest Island, off Perth.
Porpoise Bay on the southeast of the island remains closed after the head, double wrapped in a plastic bag, was found by a family as they combed the beach on Sunday afternoon.
An 11-year old girl is believed to have made the horrific discovery when she opened the plastic bag and saw a human ear.
Police on Monday confirmed the severed head belonged to a Caucasian male, aged between 30 and 50.
The man's front teeth were missing, with police saying they appear to have been removed some time before his death.
Police are treating the investigation as a murder probe, but would not detail any other wounds on the head or decomposition.
Detective Senior Sergeant Cameron Western, of WA's Major Crime Squad, said officers would pursue all avenues to identify the remains, and how they came to be on the beach, 18km off the Perth coast.
''The avenues the remains could have arrived from are limitless,'' Senior Sergeant Western said.
''But he appears to be Caucasian and missing his front upper teeth which the pathologist believes is historic and did not occur recently.''Western said the family that made the discovery was understandably shocked.
''We have put in place what we can to assist them with the feelings they are going through,'' he said.
Police said the south side of the island would remained closed while investigations continued.
Porpoise Bay has been declared a protected forensic area, with access to the public restricted.
The southern side of Rottnest Island, an idyllic WA vacation spot for generations, will be searched and police divers will search of the area where the remains were found.
''We want to make sure we do search the entire southern face of the island, which is where most of the debris washes onto that island,'' police said.
A post mortem is being conducted on the remains, while police look into the shipping movements close to the island, and water currents in the area.
People who were on boats in the bay at the time of the discovery will also be questioned.