Police say a suspect has been identified over the disappearance of a four-year-old boy who went missing in the South Australian outback.

Gus Lamont was last seen playing outside his home on a remote sheep station near Yunta, about 300km (186 miles) from Adelaide, on 27 September. His grandmother left him alone for about half an hour before checking on him, only to find the boy missing, prompting one of the largest land and air searches in the state's history.

Authorities have confirmed that a person who lives on the property has been identified as a suspect, but the boy's parents are not under investigation. In the days and weeks following the report of Gus's disappearance, police conducted extensive searches, covering about 470 sq km.

As the investigations continued, a 12-member taskforce was appointed, which sifted through family statements and identified discrepancies in the timeline of events. Police conducted a search of the property in January and seized several items including a vehicle and electronic devices. They are exploring three possible scenarios regarding Gus's disappearance: he walked off, he was abducted, or someone known to him was involved. However, given the remote location, abduction was ruled out. The investigation is ongoing, with police determined to find Gus and return him to his family.