Police have searched extensively for the missing child in the air and on the ground, with the Australian Army called in for help as the days ticked over.

As the search entered its seventh day on Friday, Assistant Commissioner Ian Parrott said police had made the tough call to scale back the search.

“Whilst we’ve all been hoping for a miracle, that miracle has not eventuated, and in the last 48 hours, despite the professional advice, it being unlikely that Gus would have survived, we have maintained and in fact increased the effort to try and locate him and bring him (back to) his family,” he said.

“We’re confident that we’ve done absolutely everything we can to locate Gus within the search area but despite our best efforts, we have not been able to locate him.”

Parrott said the search had been one of the “largest, most intense” efforts for a missing person in South Australia in recent times.

Police would not give up finding out what happened to the little boy, he said.

“We won’t stop,” he said. “We will continue to investigate and follow any lines of inquiry that we currently have.”

Despite a footprint being discovered on Tuesday night about 500m from where Gus was last seen playing, Parrott said there had been no “significant evidence” as to where he had gone.

“Everything we have found to date …. indicated that as best as we know, Gus has wandered off from this property and we have not been able to locate him,” he said.

Parrott said police were holding out hope Gus would be found alive but the chance of that was diminishing as time went on.

The little boy’s family have described him as a shy, but adventurous child and said he is a good walker, however has never left the family property before.