Police will drain a dam to rule out the possibility Gus Lamont may have drowned after he disappeared from his family's remote homestead.
Intensive searches at Oak Park Station, in South Australia's Mid North region, have failed to find any trace of the four-year-old, who went missing on September 27.
SA police plan to drain a large dam on Friday that is 600m from the homestead.
Police divers previously searched the 4.5m-deep dam in the initial days of the search.
"The draining of the dam will enable a comprehensive visual search to be completed, particularly areas with underwater vegetation," police said in a statement on Thursday.
"The renewed search of the dam is being undertaken to rule out the possibility Gus may have drowned."
An initial 10-day air and ground search at the property, about 40km south of Yunta, was one of the largest undertaken by SA Police, and the initial area covered an estimated 470 sq km.
The most recent operation, a four-day search within a 5.5km radius of the homestead earlier in October, concluded without any evidence being located.
Investigators also assessed drone data and imagery of the terrain surrounding the homestead, but had not identified any object of significance.
Further aerial imaging within a 10km radius of the homestead will take several weeks to complete.
Police said they had been hopeful the extensive ground searches would locate Gus or provide evidence of the direction in which he may have walked, but nothing was located.
"Task Force Horizon is conducting multiple lines of inquiry to locate Gus," police said.
"These investigations have not uncovered any evidence of foul play."
The boy's family continued to co-operate fully and were being supported by a victim contact officer, police said.
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