Police have scoured Umina Beach on the New South Wales Central Coast after a human jawbone was found on the sand.
A team of 10 specialist police and a cadaver dog spent more than an hour searching for clues following the find on Thursday.
Toyah Evans, 20, from the nearby suburb of Woy Woy, was walking her dogs along the beach when she made the grim discovery.
"There were teeth still in it and there was molars starting to protrude as well. It had nerve-ending parts in it," she said.
"It was very realistic and quite overwhelming."
Police said it was too early to say how long the jawbone had been on the sand or where it came from.
Keeping an open mind
Chief Inspector Steve Laksa from Brisbane Water police said the investigation would hinge on forensic analysis.
"Whether it's Australia — we are on the beach here, so we have a lot of cargo ships travelling up and down the coast," he said.
"So I think we have to keep an open mind in relation to where the bone may have come from."
Police are checking the missing person's registry and hope the jaw structure and teeth will give clues to its age.
"We don't know whether it's 12 months old or 100 years old, we just have to keep an open mind," Chief Inspector Laksa said.
The jaw was taken to Newcastle for forensic analysis, with initial examinations suggesting it had been exposed for some time.
It could be weeks before an identity is confirmed.
Police have appealed for anyone who may have seen bones in the local area and not reported it to come forward.
