From KZTV: Firefighters say a conduit, more than 50 years old, heated up under the building. The temperatures were so hot, that they started to burn the electrical wires, located at the center of the church. The boxes became engulfed with smoke, and that's when the smoke began spreading to other areas of the church.

http://www.kztv10.com/mobile/news/first-united-methodist-church-fire/