HALTOM CITY, Texas (AP) - Investigators continue seeking clues to the cause of a North Texas house fire that left a woman and three of her grandchildren dead.
    
Authorities traced the Haltom City fire's origin to the living room near a live Christmas tree. But Haltom City Emergency Management spokesman Perry Bynum said investigators still don't know what started the blaze Thursday evening or why the victims couldn't escape.
    
The woman's daughter, Yessenia Garces, lived in the house with her two children, but she was at work when the fire started. Garces said she's devastated by the loss of her mother, her 3-year-old daughter and 5-year-old son, and her 2-month-old nephew.
    
About 100 people gathered at a candlelight vigil in the Fort Worth suburb Friday night to remember the victims.