Investigators are vowing to find out what caused a deadly fire at a University of Mississippi fraternity house. Three students died in the fire yesterday at the Alpha Tau Omega house. The head of the Bureau of Alcohol, Tobacco, Firearms and Explosives office in New Orleans said today investigators will do "everything humanly possible" to find the cause of the fire. A spokesman says the university enforces fire safety policies at school residences, but not fraternity houses. The Alpha Tau Omega house had no sprinkler system. A woman who lives in student housing down the street says that while evacuation routes are posted at her building, there hasn't been a fire drill in the four years she's lived there.