Gus was last seen playing on his family’s remote homestead, about 40km south of Yunta, at about 5pm on Saturday.

The four-year-old is described as Caucasian, with long, blond, curly hair.

His family had previously declined to share an image of Gus with the media.

The military is set to join as the desperate search enters its sixth day.

He was last seen wearing a grey sun hat, a cobalt blue t-shirt featuring a yellow Minion animated character, light grey long pants, and boots.

A small footprint was found yesterday about 500m from the homestead.

Police said today a contingent of 48 personnel from the Australian Defence Force would deploy to the search area at 8am ACST today, and are expected to help with ground searches over the coming days.

Other specialised resources involved in the search include mounted and water police, dog police, PolAir, police cadets, SES volunteers, drones, an Indigenous tracker, and community and family members.

In a statement issued earlier this week, Gus’s family asked for privacy and said they were “devastated” by his disappearance.

“Gus’s absence is felt in all of us, and we miss him more than words can express,” they said.

“Our hearts are aching, and we are holding onto hope that he will be found and returned to us safely.”