PITTSBURGH—Authorities have confirmed that 3-year-old twin brothers were killed in a house fire near Pittsburgh last week, but say they don't yet know how the blaze started.

The Allegheny County medical examiner has identified the victims as Ky'heir (KY'-heer) and Dy'heir (DY'-heer) Arthur of North Braddock. One of the boys died of burns and smoke inhalation, while the other died of smoke inhalation and carbon monoxide poisoning.

The fire was reported about 3:30 p.m. Friday when a passerby saw flames, banged on the doors and called 911.

The medical examiner has yet to rule whether the deaths are accidental are homicides because a county fire marshal and other investigators haven't determined how the fire started.

Police say the boys' mother had left home to find her teenage daughter and returned minutes later to find the residence on fire.