Authorities made the discovery on the 1700 block of South Palm Avenue while searching for Oscar Javier Contreras Escobar, a self-employed truck driver last seen Aug. 28, 2012.
Police said cadaver dogs led them to the back yard area of the home, where they found charred or burnt human remains.
San Bernardino County forensics experts are analyzing bone fragments and teeth to determine if the remains belong to the 29-year-old.
Police believe foul play in Ontario may be involved in Escobar's disappearance after chasing several leads, including suspicious activity on Escobar's ATM card. The investigation eventually led detectives to the Ontario residence, where the remains were found.
The house became part of the investigation in November. Police served a search warrant on January 30. Investigators say at the time the warrant was served there were two men and a woman present at the home. They were interviewed and released.
Escobar had finished his deliveries for the day on Aug. 28, and a friend dropped him off near the intersection of Foothill Boulevard and Mango Avenue in Fontana. Escobar is from the Laguna Hills area.
The case has been deemed a homicide investigation. No arrests have been made.