A police spokesman said several shafts were relatively shallow and could be visually inspected, but the remainder were up to 20m deep and required specialist equipment to complete the searches.
Task Force Horizon and STAR Group officers searched locations on foot up to 10km from the homestead on Wednesday, which are outside the 5.5km radius previously searched, a spokesman said.
“The family of Gus have been advised of the results of the renewed searching and are being supported by a victim contact officer,” a spokesman said.
“Task Force Horizon officers have not ruled out returning to the property as the investigation continues.”
Gus was last seen playing in sand at the station about 5pm on September 27.
Dozens of police, Australian Defence members, trackers, volunteers and rescue teams scoured surrounding countryside and nearby waterways to find the boy
A ground search which covered 95sq km of the station concluded on October 17.
Police have stressed their investigations had not uncovered “any evidence of foul play”.
“The family of Gus have continued to co-operate fully with police and are being supported by a victim contact officer,” police said.
Gus was wearing a long-sleeved shirt, boots, a hat and long pants when he went missing.
Gus’s family released a statement through police on September 30, expressing their devastation at the little boy’s disappearance.
“We are devastated by the disappearance of our beloved Gus on Saturday afternoon,” the statement read.
“This has come as a shock to our family and friends, and we are struggling to comprehend what has happened.
“Gus’s absence is felt in all of us, and we miss him more than words can express. Our hearts are aching, and we are holding onto hope that he will be found and returned to us safely.
“We are incredibly grateful to the South Australia Police, emergency services and the many organisations and community members, neighbours and friends who have come together to help find Gus.”