Lucio says the toddler's mother briefly left the child alone Monday outside the family's mobile home. The child was later found unconscious.
Lucio said Tuesday that investigators at first thought the boy had inhaled gasoline fumes. The sheriff says deputies later determined a lawn mower's gas cap was removed and some type of tube or pipe had been in the fuel tank, leading to an investigation into whether the boy drank the gasoline.
An autopsy has been ordered.