Police in Uniontown, Ala., said they received the call at about 1:30 a.m. Wednesday. A mobile home on Long Street was fully engulfed by fire.
Uniontown Police Chief Donald Rhodes said a female relative tried to get into the trailer and save the family, but couldn't.
Police identified the dead as Viola Fikes and her children: Emmanuel Lane, 9; Wyquise Fikes, 6; Shakerria Ward, 4; and Sekira Fikes, 1.
Investigators from the state Fire Marshal's office are trying to determine how the deadly blaze got started.
Assistant State Fire Marshal Ed Paulk said it will take several days for the investigation and autopsies to be completed. He said he was told neighbors spotted the fire and that the trailer had no electricity.
Uniontown is located in southwest Perry County, about 90 miles west of Montgomery.