Police investigating the murder of a man whose head was found on Rottnest Island are sifting through missing persons files across Australia as they try to identify him.
Officers and State Emergency Service volunteers searched the island yesterday after an 11-year-old girl found the head wrapped inside two plastic bags at Porpoise Bay, on the south-east of the island, about 4pm on Sunday.
The girl was beachcombing with her family when she found a bulky item inside a plastic bag.
The family spotted a human ear when they opened the bag and immediately called police.
Forensic and major crime squad officers travelled to the island on Sunday and the remains were sent to the State mortuary for further examination.
The State pathologist told major crime squad detectives yesterday that the head was believed to be that of a Caucasian man aged 30 to 50, although the age range was not certain.
Det-Sen. Sgt Cameron Western, of the major crime squad, said the man had no piercings and appeared to be missing his upper front teeth.
The State pathologist told police the teeth had been missing for some time.
The discovery prompted police to declare Porpoise Bay a protected forensic area, meaning holidaymakers are banned.
Police will search the southern side of the island and divers will scour the ocean over coming days.
Police will examine ocean currents and boating movements near the island over recent days.
Sen. Sgt Western said detectives were liaising with ocean experts, including officers from the water police, regarding ocean currents.
State Emergency Service volunteers and police plan to scour the southern end of Rottnest Island where debris tends to gather.
Porpoise Bay is sheltered by reefs but debris often washes up on the beach
"We're conducting investigations to determine the currents surrounding that area but the avenues they could have arrived from are limitless," he said.
Sen. Sgt Western said detectives had identified boats that were in the area at the time the remains were found and would speak to the occupants.
Detectives were also scouring missing persons reports from WA and other States. He would not comment on other injuries to the head.
Sen. Sgt Western said the family who made the discovery were shocked.
"We have put in place what we can to assist them with the feelings they are going through," he said.
Police will use forensic techniques to identify the man and are treating the discovery as a homicide investigation.
They have appealed for anyone with information regarding the identity of the man or the discovery to contact Crime Stoppers on 1800 333 000.