Lori Vallow was arrested in Hawaii last week on an Idaho warrant. Her two children, 7 and 17, have not been seen since September.
It was not immediately clear what caused the fire in the city of Carson. Local residents reported hearing an explosion and seeing a fireball.
The girl, Evelyn Mae Boswell, remains missing. The sheriff has said that the mother gave information that was not thought to be accurate.
He said he's been "targeted by staff,” “verbally harassed and abused without cause” and “treated disproportionately harsh" as a federal inmate.
Michael Joseph Honkomp, 30, was shot in an exchange of gunfire with police and has been charged with murder and other counts.