Police have made the tough decision to scale back the search for a four-year-old boy who went missing from his home in South Australia’s outback, saying they have been unable to uncover any significant clues as to where he may have gone.

Australian Defence Force personnel arrived on Thursday to join the search at the remote sheep station about 300km north of Adelaide where little Gus went missing six days ago, with a specialist Aboriginal tracker also called in to help.

But while the discovery of a small footprint within 500m of the family home offered a glimmer of hope earlier in the week, police have since said it could be more than a week old.

SA Police Assistant Commissioner Ian Parrott said on Friday that no further significant evidence had been found to indicate a direction for the searchers to focus on.

“Whilst we’ve all been hoping for a miracle, that miracle has not eventuated,” he told reporters.

Gus, described as an adventurous boy, had been playing in the sand at the family homestead near Yunta when he disappeared on Saturday.

Since then, there have been extensive ground searches involving State Emergency Service volunteers on trail bikes, all-terrain vehicles, dogs and a drone, as well as helicopters, police divers and mounted officers.

“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, and unfortunately, we are now having to scale back this search for Gus,” Commissioner Parrott said.

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

Specialist water teams were called in during the search. Photo: SA Police

Parrott said the search was “one of the largest and most intensive” conducted for a missing person in South Australia in recent times.

Throughout, police have remained confident the little boy left the area on foot, leading them to focus on a 3km radius from the home.

While it was unlikely he could have survived so many days alone and without food, until now they held onto the slim hope he may have crawled into a shelter and was waiting to be rescued.

Nonetheless, Superintendent Mark Syrus told ABC Radio on Wednesday that they had prepared his family for the worst-case scenario.

“This is a young boy without food, water, shelter for that period of time, so it is going to be pretty tough on that little lad,” Syrus said.

“We’re preparing the family for the fact that we may be moving from a search effort to a recovery.”

Gus’s distraught family broke their silence on Tuesday, saying they were devastated by his disappearance and still holding onto hope he would be returned safely.

“This has come as a shock to our family and friends, and we are struggling to comprehend what has happened,” they said.

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

On Thursday, the family released a photo of the blond, curly-haired pre-schooler wearing a Peppa Pig top with the words “My Mummy”.

Senior Constable Peter Williams told ABC Radio Adelaide that police had been inundated with calls since the photo was published, but many were from people offering unwelcome speculation rather than information that could assist the investigation.

“If it is just an opinion, perhaps keep it to yourself, but if you’ve got factual information, feel free to give us a call and provide that.”

SA media reported that while there were still searchers at the family property on Friday, their presence was significantly reduced.