Fire investigators say improperly disposed smoking material caused Sunday afternoon fire in Durham. Fifteen fire trucks responded to a two-story, wood-frame house just after 4 p.m. Officials said they were originally called to an outside fire, but it was upgraded to a structure fire. When they arrived, there was fire on the outside of the house involving the siding. A Mazda car had heat damage from the fire. No one was injured. Firefighters said there was not an extension of fire into the house.