Search for missing boy resumes in major-crime probe

Four--year-old Gus Lamont was last seen playing outside a remote property in September. (HANDOUT/SA POLICE)

The search for a missing four-year-old has resumed after police declared the boy's disappearance a major crime and indicated they had identified a possible suspect.

Gus Lamont was last seen by his grandmother playing at the Oak Park Station homestead in outback South Australia on September 27.