The sheriff's coroner's division said it suspects the death was a suicide due to asphyxia, but the cause of death is still under investigation.
Last month, the "Good Will Hunting" actor, who has struggled with addiction in the past, entered a Minnesota rehabilitation center to help him maintain sobriety.
His representatives at the time said Williams was not using drugs or alcohol but had gone to the center to "fine-tune and focus" his sobriety after working a longer-than-usual schedule.