No evidence has been uncovered during the second day of a renewed search for missing four-year-old Gus Lamont.

Australian soldiers, police officers and SES volunteers have trekked between 20 and 25 kilometres per day in hot outback conditions to search for Gus.

Extreme heat and strong winds is forecast to hamper efforts tomorrow and the search will start at sunrise before being called off at midday.

Missing four-year-old Gus was last seen on September 27. (South Australia Police)

Gus was last seen about 5pm on Saturday, September 27 at his family’s homestead Oak Park Station in remote South Australia, about 40km south of Yunta.

Police, along with Australian Defence Force (ADF) personnel, yesterday returned to outback SA and launched Taskforce Horizon to investigate Gus’ disappearance after no trace of Gus was found in an initial six-day search.

No evidence was uncovered during yesterday’s efforts either, police said.

The search has now extended to zones outside of the original search area.

It is expected extreme heat conditions tomorrow afternoon may restrict the search, police said.

Temperatures are forecast to reach tops of 36 degrees in the Yunta area tomorrow.

Officers and soldiers will continue the search during the cooler morning period.

The temperature reached a top of 30 today.

Eighteen police officers, 84 ADF personnel, 33 cars, SES resources, drones and utility terrain vehicles are being used are to scour the remote terrain in SA’s mid-north.

ADF soldiers joined the renewed search yesterday and today. (9News)

SA Police Commissioner Grant Stevens said yesterday no stone would be left unturned in the search for Gus.

“We are dedicated to making sure we do everything we possibly can to bring Gus back to his family,” Stevens said.

The fresh search was not triggered by any new information, Stevens said.

“We are looking for up to two days but there will be a continual reassessment,” Stevens said.

“The resources that we’re deploying may change over time and the use of specialist drones will be another consideration as we move forward as well.”

The search area covered so far has been around 470 square kilometres.

Stevens emphasised the sheer magnitude of the search area and said it was like combing through “100 Adelaide CBDs”.

“We are searching in quite unusual terrain, it is a significant effort,” he said.

“We’re exhausting every opportunity to recover Gus.”

Temperatures are forecast to reach tops of 36 degrees in the Yunta area tomorrow. (9News)

Taskforce Horizon consists of 12 specialists who will analyse information and suggest different areas to search.

Stevens told reporters there is nothing to suggest foul play in Gus’ disappearance.

Police have received more than 150 Crime Stoppers tips since Gus went missing, but warn online speculation has been hurtful to Gus’ family.

His family have said in a statement they are “devastated” and “deeply distressed” by his disappearance.

“I would describe them as stoic,” Stevens added.

“But you can imagine just how they are feelings, without having Gus and without having answers to exactly where Gus is and what’s happened to him.

“This would be traumatic for any family.”