Fire investigators in south Georgia Friday were trying to determine what sparked a blaze at a home in Tifton that left twin 12-year-old brothers dead.

The fire, which was reported about 1:30 a.m., destroyed the family’s single-story home in the 600 block of Timmons Drive, according to Glenn Allen, spokesman for state Insurance and Fire Commissioner Ralph Hudgens’ office.

Allen said Jeremiah and Nehemiah Walker died in the fire. Both boys were autistic, and that might have contributed to them being unable to escape the blaze, according to Allen.

The boys’ mother, 44-year-old Tangela Walker, and their 15-year-old sister, Florissa Walker, escaped without serious injury.

Allen said his office was also investigating a second fatal overnight fire in Houston County south of Macon. Opal Alford, 86, died in that blaze, which was reported about 7:25 a.m. in the 100 block of Lonesome Doe Circle in Kathleen, Ga.

“The fire has been determined to be accidental and it was caused by unattended cooking,” Allen told The Atlanta Journal-Constitution. “A neighbor or bystander was able to enter the home and remove (Alford) from the home, but she died on the scene.”