Criminal experts believe a “third party” is involved with the disappearance of Gus Lamont after police were forced to scale back the search this week for the missing four-year-old in remote South Australia.

Augustus “Gus” Lamont was last seen by his grandmother playing in the sand in a Minions t-shirt at his family sheep station near the town of Yunta on September 27 about 5pm. When she went to call him inside about half an hour later, the preschooler was nowhere to be seen.

Police were forced to scale back the search on Tuesday after a major 10-day effort involving helicopters, drones, and Aboriginal trackers failed to yield any clues into the child’s disappearance.

Four-year-old Augustus “Gus” Lamont. Picture: Supplied

A single footprint found in the search for the boy. It was later ruled out by police as being part of the search. Picture: Supplied
Speaking to news.com.au, criminologist Xanthe Mallett said all signs now pointed to a third party involvement.

“Given he’s so young, it’s very unlikely that he would have run away. That’s more a teenager kind of thing,” she said.

“The scale of the search and how detailed it was, and the drones and everything else, it does feel at this stage, sadly, that if they haven’t found something that it’s likely to be third-party involvement.”

Very little was found in the 10 search except for a “small boot print” found near a dam.

However, the footprint was later ruled out with police saying it was not related to the search.

Ms Mallett said given the “remote” nature of the area near Oak Park Station, the lack of evidence found in the search also points to a third party.

The property near Yunta where 4yo boy Gus Lamont went missing. Picture: 7NEWS Adelaide
“When they were looking for Dezi Freeman, that was a really hard environment to search by plane or drone because it’s such dense bushland, whereas this isn’t that kind of scenario,” she said.

“If he were wandering or had fallen, then the technology and the search strategies they’ve applied should have located him.

“The fact they’ve scaled back means that they feel that they have searched well enough to do that. So, it does feel sadly like that there’s probably somebody else involved.”

Next stage of investigation

Police believe Gus was living at the remote homestead with his mother Jess, his one-year-old brother Ronnie and his grandparents.

A family member from the homestead speak to police at Oak Park Station. Picture: 7NEWS Adelaide
It is believed Gus’ father Joshua lives in Blalie North near Jamestown – about 100km west of the homestead.

None of Gus’ family members is accused of any wrongdoing or involvement in his disappearance.

Speaking generally about missing children’s cases, Ms Mallett said police are likely to start looking into those “physically present” at the time of Gus’ disappearance.

“Especially with young children, they will look at those family dynamics,” she said.

Phone tower pings

Ms Mallett also said that one major component of the case, which will assist police is the lack of phone towers in the remote area.

In the case of Cleo Smith, who was taken from a campsite in WA, a single ping to a phone tower – which was only built in 2018 – helped lead police to the phone of her kidnapper, Terence Darrell Kelly.

“There won’t [have been] that many people in that area,” Ms Mallett.

“So those people whose phones do ping, [police will] be able to track down and speak to.”

William Tyrrell lead detective weighs in

Former homicide squad detective Gary Jubelin is also of the opinion that another person is involved in the Gus Lamont case.

Mr Jubelin said that the fact police were looking at third-person intervention was a learning lesson from the William Tyrrell investigation, in which he said the “whole focus was on finding the little boy lost”.

“Children disappearing at that age is a rare event,” he told Nine’s Today show on Wednesday.

“What police would be looking for is, has the disappearance been the result of wandering off, misadventure and getting lost, or is there some form of intervention involved in his disappearance?

“What I’m seeing now and what I’m reading between the lines of what South Australian Police (are doing), they’re looking at other possibilities that there was perhaps intervention. So it’s difficult for the families involved and even for the police.”

On Tuesday, Deputy Commissioner Linda Williams revealed the case had been moved to the Missing Persons Section.

Police and Gus’ family say they have not given up hope. Picture: 7NEWS Adelaide
“The investigation is now being managed by Missing Persons Section, which is part of Major Crime Investigation Branch, and that’s where all long-term cases such as this are managed and investigated,” Commissioner Williams said.

“We will never give up hope of finding Gus.

“There are further lines of enquiry being undertaken and the family have continued to co-operate with fully with police.”

Police earlier deployed a special drone in the search, with Ms Williams confirming the “significant aerial search” involved a special drone with infra-red capabilities.