The federal Bureau of Alcohol, Tobacco, Firearms and Explosives is working with Kalamazoo investigators to determine the cause of a fire last week that killed three young children.

TV stations WWMT and WOOD report ATF investigators were at the scene Monday. Officials hope to determine a cause by later in the week.

Police say 3-year-old twins Tevin and Ty'nitha Williams and their 1-year-old sister Tyonna Henderson were killed in the Feb. 18 fire at the low-income apartment building. Officials say the children were left home alone. Their 4-year-old sister has been removed from her mother's custody.