Officials in Miles City say a man who had escaped a house fire died when he went back into the burning building in an unsuccessful effort to rescue his sister.

Custer County Coroner Tony Harbaugh identified the victims of Wednesday's fire as 51-year-old Brian Donnelly and 56-year-old Dianne Donnelly.

Officials say Donnelly, his wife Laura and son Brandon initially escaped the blaze, which was reported at about 3 a.m.

Fire Chief Dale Berg said Laura Donnelly told him the family was caring for Dianne Donnelly, who had dementia.

A state fire marshal was helping to investigate the cause of the fire, which burned for about two hours, destroying the home's interior.

Berg said one firefighter was treated for respiratory problems and released from the hospital.