HARGILL, Texas -

A mobile home fire that killed three young children in South Texas was likely accidental and caused by an electrical problem, a sheriff said Monday.

A preliminary investigation found no evidence of accelerants that would suggest arson caused the Sunday fire, which reduced two adjoined mobile homes to ashes and twisted metal, said Hidalgo County Sheriff Lupe Trevino. Investigators also don't believe space heaters were to blame.

Trevino said the likely cause was electrical and he speculated that the family, three generations of which shared the trailers, may have been running extension cords from one to the other.

"A statement from the 19-year-old father actually says that he was awoken by noises, by smoke and then he sees an outlet, maybe a fuse box that is sparking," Trevino said.

Killed in the fire were 15-day-old Victorino Robledo, 1-year-old Angelica Robledo and 3-year-old Salvador Robledo, who shared the name with his father, Trevino said.

The father, Salvador Robledo, was taken to Brooke Army Medical Center in San Antonio along with his wife Angelica Reyes, 20, and his father Santiago Robledo, who helped rescue them from the fire.

Trevino said they were being treated for burns and smoke inhalation, but he did not have information on their conditions. Phone messages left to at the medical center by The Associated Press were not immediately returned.

The trailers, which sat on a corner lot in the rural community of Hargill about 225 miles south of San Antonio, were engulfed in flames when firefighters arrived shortly after 5 a.m. Sunday.

On Monday, yellow fire boundary tape surrounded the site. A chicken scratched through the ash on what appeared to be the foundation of one of the mobile homes. Cactus, palm trees and a fence ringing the property were charred.