A preliminary autopsy report shows the heat killed two young East Tennessee brothers who died last week.
The Bradley County Sheriff's Department released no other details about the deaths of 5-year-old Leland Bates and 3-year-old River Bates.
Officials responded to a call last week from the boys' mother who reported a near-drowning, but no pool or body of water was at the scene.
The youngest boy died that day. The older child died later at a Chattanooga hospital.
The sheriff's office says criminal investigators continue to work the case.