The likelihood of finding a little boy lost in the outback is fading as family and searchers cling to hopes he has found shelter and is waiting to be rescued.
Defence personnel have joined the search for the four-year-old who has not been seen for almost a week.
August, known as Gus, went missing from his family's sheep station in the remote South Australian mid-north on Saturday afternoon.
The only trace found of the preschooler is a tiny footprint in the dirt about 500 metres from the family homestead, which brought hope, but police now admit it "could have been there a week".
"A four-year-old lad, they just don't disappear into thin air," superintendent Mark Syrus said on Thursday.
"They have to be somewhere, so our job is to try and find which way he has gone and once we find those little clues, it gives us a bit of an idea."
Searchers turned their efforts to the homestead area after the footprint was found, but no further clues were found about where Gus went or could be.
"Unfortunately, we didn't find anything at all, so we're continuing back out to the search area and just hoping that we can find him," Syrus said.
The search was expanded as almost 50 Australian Defence Force personnel joined the operation.
The extensive search for the missing boy has involved SES volunteers on trailbikes, ATVs, dogs and a drone. Source: Supplied / Channel Seven
But hope is fading and police have prepared the family for the worst as the search shifts from a rescue to a recovery operation.
"Hopefully, he's hanging in there and alive, but we (are) in the recovery phase," Syrus said.
"The fact that he's been gone for over 100 hours, six days, that's a long time for a young boy to be out in the elements."
The lack of evidence has prompted police to expand the search area beyond a 2.5km circumference around the homestead "to areas of higher probability".
"We're going to be walking the next couple days, we'll still have the police helicopter, we'll still have the mounted here continuing on the search, hoping that Gus has crawled into a hole somewhere and he's just still hanging in there," Syrus said.
The preschooler's distraught family spoke earlier in the week, saying they were "struggling to comprehend what has happened" to the youngster.
The adventurous boy had been playing in the sand near the family homestead when he disappeared.
Extensive searches involving State Emergency Service volunteers on trail bikes, all-terrain vehicles, dogs and a drone have been carried out and helicopters, police divers and mounted officers have been involved.
Police cadets, SES volunteers, an Aboriginal tracker and a large number of community and family members have bolstered the search effort.
Police have said they do not believe the disappearance is suspicious.
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.
