Police believe Blewitt, who was last seen on April 12, 2004, in Melton, was part of the hit team that killed underworld figure Graham "The Munster" Kinniburgh in 2003.

That slaying was, police believe, ordered by drug kingpin Carl Williams as part of his war against the Moran crime family.

Blewitt, a career criminal who specialised in armoured car robberies, is thought to have shot dead a security guard outside a Sydney bank in 1994.

Purana Taskforce detectives found what could well be Blewitt's remains during a search of a property in Pelmet Crescent, Thomastown in Melbourne's north.

Purana Detective Inspector Andrew Gustke said a human skeleton had been found but it might be weeks before dental records could confirm its identity.

At this stage, Detective Inspector Gustke said, police were "keeping an open mind" about identification.

Police spokeswoman Kelly Grindley said detectives have been searching and digging at the  property since Monday morning, finding the remains late on Wednesday afternoon.

"While the human remains are yet to be formally identified, detectives believe they are that of missing man Terrence Blewitt," she said.

Archeologists have been at the site since the police excavation started on Monday morning.

The human remains were found about three metres below the surface.

The excavation had been a "slow and painful" process, with the 30-tonne excavator used in the initial dig now replaced by hand searches.

About 4000 cubic metres of soil has been shifted in the search of the site, which was a scrapyard until about 2006.

The scrapyard was subsequently covered with landfill.

The site's former owner, who has has died of natural causes, may be implicated in the dumping of bodies on the site, Detective Inspector Gustke said.

"The current owner of the property has no connection to the investigation."

It is not believed Blewitt was killed at the Pelmet Crescent site, which is in an industrial estate.

Ms Grindley said a search was generated by police intelligence and information received by the investigating members.

Archaeologists have joined the police search for the remains of Terrence Blewitt. Photo: Justin McManus

Detectives are hoping the search will also  provide further evidence in relation to Kinniburgh's murder, she said, though Detective Inspector Gustke would not confirm what evidence had so far come to light.

The investigation has been the longest murder probe conducted by Purana.

"Purana Taskforce investigators have taken hundreds of statements and interviewed hundreds of people during these investigations," Detective Inspector Gustke said.

Underworld figure Graham Kinniburgh was murdered in Kew in 2003. Police have long believed there was a connection with the disappearance of Terrence Blewitt. Photo: Andrew De La Rue

The reward of $100,000 offered for information about Kinniburgh's murder had not been a factor.

"Organised crime has a wall of silence that sometimes takes many years to penetrate," Detective Inspector Gustke said.

"That wall of silence is only broken down by individuals in the community, so we do ask for people that may have seen Terrence Blewitt in early 2004 to please come forward."

Detective Inspector Gustke said the investigation has been complex and protracted. 

"We owe it to the family and friends of any victim of crime to investigate and do our very best to bring out some justice for them, and that's what we are hoping to achieve with this discovery."

Detective Inspector Gustke said he had been in contact with Blewitt's family about the discovery.

"I feel for Mr Blewitt's family ... and friends and loved ones," he said.

Police are expected to remain at the site for several days, but Detective Inspector Gustke said they were concerned about an impending downpour forecast for Friday that could hamper their efforts. 

Gangland hit

Kinniburgh, 63, had parked his car and was walking to his two-storey house on December 13, 2003, when he was gunned down.

He was a lifelong friend of Judy Moran and her former husband Lewis.

Mick Gatto was a pallbearer at his funeral.

Kinniburgh was considered an influential standover man, who had convictions for dishonesty, bribery, possession of firearms, resisting arrest and assaulting police.

Kinniburgh was implicated by a coroner in 2002, along with Jason Moran, in the death of gangster Alphonse Gangitano in 1998.

The burnt getaway car used by gunmen to shoot Graham Kinniburgh. Photo: Joe Castro

Williams, bashed to death in Barwon Prison in 2010, always denied any connection to the Kinniburgh murder.

"My conscience is clear," Williams told The Age less than 48 hours after the killing.

"I've never met him and I've never heard a bad thing said about him. I have nothing to profit from his death. It's a mystery to me."

In mid-2013, police seized a blue Hyundai Excel which had been linked to the slaying of Kinniburgh and Blewitt.

On the day the car was seized in Alexandra, a $100,000 reward for information regarding Kinniburgh's murder was announced.

Police charged Stephen John Asling with Kinniburgh's killing in November.

Blewitt has not been seen since he was spotted walking towards a similar car on April 12, 2004, in Melton.

A similar car had  reportedly been seen leaving Belmont Avenue in Kew shortly after Kinniburgh was shot.

Career criminal

Blewitt specialised in armoured car robberies. In the mid-1980s, he was jailed in Sydney after shooting a cash-in-transit security guard.

In 1994  he was part of a home invasion and attempted armed robbery in which a young Coffs Harbour couple were terrorised in their bedroom at gunpoint.

Sydney security guard Robert Jones was killed by Blewitt in 1995.

A year later Blewitt  is believed to have shot dead security guard Robert Jones outside the Westpac Bank in the Sydney suburb of Miranda.

An accomplice told Fairfax Media in 2014 that he'd given a detailed confession, naming Blewitt as the killer, to NSW Police in 2000, but they had not acted on the information.

In 2000, he was sentenced to six years' jail with a minimum of three for conspiracy to commit an armed robbery.

He was released shortly before Kinniburgh's murder and in 2004 was arrested again for the armed robbery of a cash handler making a midnight deposit at a Mornington bank.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report at www.crimestoppersvic.com.au.

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