The grandparents of Gus Lamont have issued a statement a day after police confirmed they have a suspect and declared the disappearance of the four‑year‑old a major crime.

Police said the case is formally a major crime more than four months after Gus vanished from a remote Yunta sheep station on September 27.

In a joint comment shared by their lawyers, Josie Murray and Shannon Murray said they were “devastated” by the announcement.

“We are absolutely devastated by the media release of SAPOL Major Crime,” they said.

“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 comments come after police said the person of interest is not either of Gus’s parents, however, “inconsistencies and discrepancies” were found in the information provided by other family members.

Gus was last seen playing outside the Oak Park homestead (pictured) while his grandmother cared for his younger brother inside.Gus was last seen playing outside the Oak Park homestead (pictured) while his grandmother cared for his younger brother inside. Credit: 7NEWS Dams on the property were searched multiple times in the search for Gus.Dams on the property were searched multiple times in the search for Gus. Credit: AAP

“As a result, a person who resides at Oak Park Station has withdrawn their support for police and is no longer cooperating,” Detective Superintendent Darren Fielke said on Thursday.

“That person is now considered a suspect in the disappearance of Gus.

“A comprehensive forensic search was conducted of the Oak Park Station homestead, and a number of items were seized, including a vehicle, a motorcycle and electronic devices.”

The grandparents have both hired separate lawyers, with the legal firms saying “Andrew Ey and Casey Isaacs can confirm that we act for Josie Murray and Shannon Murray respectively”.

They also confirmed their clients would not be be participating in any interviews or commenting any further on the investigation except for the brief joint comment.

Gus was last seen playing outside the Oak Park homestead while his grandmother cared for his younger brother inside, according to his family.

At 5.30pm when his grandmother went outside to call him in, Gus was gone.

Extensive searches over several months involving police, SES volunteers, army personnel, drones and helicopters and Indigenous trackers have proven fruitless during eight separate large scale searches.

A single footprint discovered about 500m from the property is the only physical clue believed to have been found of Gus.

Police said the major crime declaration reflects the seriousness of the investigation, and that they were confident Gus didn’t walk off on his own.