Fire investigators are not sure what caused a house fire that occurred Saturday morning in Jefferson City. Fire department reports show the fire at 1410 East Miller Street was called in around 6:30 a.m. When crews arrived on the scene they found heavy smoke and flames coming from the rear of the building. They also had to rescue two residents of the home who had gone out on the first floor roof to escape the fire. Prior to the arrival of firefighters, some teenage residents did jump from the roof to escape, but had no reported injuries. After the fire was put out, investigators determined the blaze began in a bedroom that was built as an addition in the rear of the structure. It was unoccupied at the time of the fire. As of Saturday afternoon, fire officials said they were listing the cause as accidental, although they weren't sure what caused the fire, and they said they had no reason to believe there was anything suspicious about the fire.