Police are investigating how a man suffered fatal injuries at a Hunter rubbish tip after closing time on Sunday.
A post-mortem was expected to take place on Monday afternoon or Tuesday on the body of 54-year-old Shane Mears, who suffered what a senior detective described as " multiple, significant injuries".
"We believe those injuries have led to the man's death," Detective Inspector Matt Zimmer said.
"Until we know the exact circumstances of what's happened and the cause of death, we are treating the death as suspicious."
Inspector Zimmer would not be drawn on Monday on whether the incident was a homicide, but Australian Community Media understands police do not believe it likely the 54-year-old met with misadventure.
Investigators are waiting for the results of the post-mortem to determine the full extent of Mr Mears' injuries - Australian Community Media understands they are particularly interested in learning more about injuries to his head.
Police are investigating the possibility Mr Mears and a friend sneaked into Cessnock Waste Management Centre via a bush track and whether they were there to steal from the scrap metal and white goods section of the dump.
The friend - a 46-year-old man from Cessnock - has been helping police with their inquiries.
He had not been arrested and the Herald understands he was not a suspect at the time of publication.
Investigators believe the pair came across other people at the tip before Mr Mears suffered his fatal injuries.
"We do believe there were other people in the vicinity of where the deceased male was, shortly prior to his death," Inspector Zimmer said.
"Those people are unknown to us at this stage."
Police were called to the Old Maitland Road tip just after 5pm on Sunday after reports a man had been critically injured.
There, they found the 54-year-old - who died at the scene.
Detectives set up Strike Force Nargal to investigate the incident.
A forensic examination of the site began on Sunday night and continued into Monday, with police focusing on what appeared to be two separate areas separated by a large mound of scrap metal.
"It's quite a remote area, where the deceased was located," Inspector Zimmer said.
"There's a lot of bushland surrounding that particular area."
Mr Mears was previously known to police and Inspector Zimmer said the Cessnock man's "background and associations" would be looked into as part of the investigation.
He said police were working to identify the other people who were inside the grounds of the dump when the 54-year-old was injured, and he called on anyone with information to come forward.
"We are still in the early stages of this investigation," he said.
"We are still trying to establish the circumstances surrounding the man's death. We are asking anyone with information to contact [police]."
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