Investigators may never know for certain what sparked the fire on the left side of the U-shaped assisted living facility.

The cause of a deadly fire​ at the Gabriel House assisted living home in Fall River, Massachusetts has been narrowed to two possibilities.

More information on the cause of the deadly Fall River fire at Gabriel House on July 13 was released Tuesday. During a press conference Tuesday afternoon, officials said evidence narrowed the cause down to two possibilities, either an electrical or mechanical failure of an oxygen concentrator or the improper use or disposal of smoking materials.