A new police search for evidence into the disappearance of Gus Lamont at a rural South Australian station will focus on dried-out creeks and waterways that were flooded during the previous visit by investigators to the property.

Police have said they are returning to Oak Park Station for the next three days to search parts of the property for any evidence that may shed light on the disappearance of the four-year-old in September last year.

The search, which Major Crime detectives and specialist officers will conduct, is set to take advantage of the recent heavy rain, which may help in the search for clues into his disappearance.

9News understands police hope the recent rains may have uncovered evidence, including clothing that Gus was wearing at the time of his disappearance eight months ago, such as a large-brimmed hat and a Minions shirt.

Police are focusing on sites that were inaccessible during their previous visit to the property in March, when flooding was taking place.

Authorities have said an update will be provided as the investigations continue.

Gus' disappearance is being considered a major crime by South Australian police.

South Australian police have repeatedly said that Gus's parents are not considered suspects in his disappearance.

In February, police confirmed a person with close ties to the household, who is not one of Gus' parents, had been speaking with detectives but then allegedly "withdrew cooperation" and has since been identified as a suspect.

During investigations, police charged his 75-year-old grandparent, Josie Murray, with firearms offences, but emphasised that the charges were not linked to the four-year-old's disappearance.

Josie Murray and Gus' other grandparent, Shannon Murray, released a statement through their lawyers, saying they were "absolutely devastated" by SA Police's statement on February 6.

"We are absolutely devastated by the media release of SAPOL Major Crime. The family has cooperated fully with the investigation and want nothing more than to find Gus and reunite him with his mum and dad," the statement read.

The lawyers also indicated they will not be making any further comments.

There is no suggestion that Josie or Shannon Murray is involved in the disappearance of Gus, and it is not unusual for anyone linked to an investigation to seek out legal advice.

Gus was last seen playing on a dirt mound at Oak Park Station around 5pm on September 27.

Following his disappearance, a full-scale ground and air search of the property and the surrounding area was launched.

No evidence of Gus has been uncovered despite extensive searches of the property, which Detective Superintendent Darren Fielke said has been the "largest and most intensive" missing person search ever undertaken by SA Police.

The most recent search was called off in March after police were unable to find any new evidence, despite heavy rainfall in the area.

The multi-agency search for the missing toddler has expanded more than 700 square kilometres with the assistance of 80 Australian Defence Force soldiers, drones, mounted officers and aircraft.

More than 160 South Australian police officers have also been deployed, and authorities have received more than 150 tips about the missing boy since February.

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