South Australia police declared the disappearance of four-year-old Gus Lamont a major crime on Thursday and named a person living with him as a suspect. Gus vanished from his family’s outback home at Oak Park station, near Yunta, over four months ago. This sparked one of the biggest search efforts ever seen in the region. Detective Superintendent Darren Fielke said police ruled out Gus wandering off or being abducted. Instead, they are investigating someone in the household who is not one of Gus’s parents. "We have identified a number of inconsistencies and discrepancies in the information from family members," he stated. Fielke added, "A person who resides at Oak Park station has withdrawn their support for the police and is no longer cooperating with us. The person who has withdrawn their co-operation is now considered a suspect in the disappearance of Gus. I do want to stress, however, that Gus’s parents are not suspects in his disappearance." The boy was last seen playing outside the family sheep station on September 27, wearing a blue T-shirt with a yellow Minion, a grey sun hat, long grey pants, and boots. When his grandmother went to call him inside 30 minutes later, he was gone. Police and emergency teams searched the 60,000-hectare Oak Park station for months. They used mounted police, divers, drones, and trackers. They drained a dam and examined abandoned mine shafts. Despite the vast effort, no clues led to Gus. The investigation is ongoing with no stone left unturned, said Fielke. "We’ll continue to thoroughly and meticulously investigate the disappearance of Gus until we get an outcome," he added.