Gus Lamont. (Source: South Australia Police)

Police on Tuesday expanded their search for Gus Lamont, who went missing at the Oak Park Station homestead about 40km south of Yunta, in South Australia’s Mid North region on September 27.

SA Police Commissioner Grant Stevens says there is no evidence Gus met with criminality and the task force was aimed at expanding the search area around the property for the missing child.

“There is no evidence to suggest any other circumstances that might have resulted in Gus not being located,” he told reporters on Tuesday.

“Our focus is largely on an exhaustive search of the property, on the basis that Gus has wandered off, and we’re hopeful that we can find him and return him to his family.

“But we also have an obligation to consider all possibilities, and that’s part of our work going forward, is to make sure that nothing is left unaddressed.”

About 80 defence force personal have joined police in the fresh search for the preschooler.

The initial search, which covered approximately 470 sq km, ended about a week after the boy went missing.

SA Police launches Taskforce Horizon in Gus Lamont search at Yunta | The Advertiser

“We are looking for up to two days, but there’ll be a continual reassessment, and the resources that we’re deploying may change over time, and the use of specialist drones will be another consideration as we move forward as well,” Stevens said.

Gus’s family remain stoic and are co-operating with investigators, he said.

“But you can imagine just how they’re feeling without having Gus and without having answers as to exactly where Gus is and what’s happened to him,” Stevens said.

“This would be traumatic for any family.”

Taskforce Horizon was made up of 12 specialists, who would analyse information from the search and provide advice.

“Search co-ordinator specialists, medical specialists and survivability specialists, looking at every possibility, and this is us exhausting those possibilities,” Stevens said.

Search for missing four-year-old Gus expanded in South Australia's mid-north

Gus’ grandmother was the last to see him, playing on a mound of dirt at 5pm on the day he disappeared. The boy was described as shy and adventurous.

Police scaled back the search after hundreds of police, defence personnel and volunteers scoured the property for almost a week in late September and early October.

Gus has long, blond, curly hair and was last seen wearing a grey sun hat, a blue T-shirt with a yellow Minion on the front, light-grey long pants and boots.