Fire investigators in DeKalb County Thursday were still trying to determine what sparked the Saturday night house fire that killed an Avondale Estates mother and daughter.

The two were killed in a fire that broke out Saturday night in the family's home on Lakeshore Drive in Avondale Estates.

Tami Willadsen's 5-year-old son, Jack, suffered serious burns, and husband Dave, sustained minor injuries in the fire.

DeKalb fire Capt. Eric Jackson told The Atlanta Journal-Constitution Thursday morning that the cause of the fire had not yet been determined.