The fatal Sunday morning fire in Millen has been ruled "undetermined," according to Georgia Insurance and Safety Fire Commissioner Ralph Hudgens.

Joshua Christopher Trent Buckley, 14, was killed in the blaze, which was reported at about 5 a.m. Sunday. The mobile home, at 1658 U.S. Highway 25, was destroyed.

"My investigator believes that this was an accidental fire, but because of extensive damage to the mobile home, he was unable to determine the exact cause," Hudgens said in a news release issued Thursday. "One of three electrical space heaters found in the bedroom with the deceased may have malfunctioned and started the blaze."

The results of a preliminary autopsy showed that Buckley died of smoke and soot inhalation, the release says.

The Millen Fire Department, Jenkins County Fire Department, and Jenkins County Sheriff's Office worked with Hudgens' office on the case.