Officials say a house fire late Saturday morning in Shenandoah was likely caused by a defective heat lamp. According to reports, firefighters were called to 705 south Center Street at around 11:15-a.m., Saturday. When they arrived, the exterior of the home was engulfed in flames. Damage to the structure was primarily limited to outside of the home, with the inside sustaining smoke damage. The structure was unoccupied at the time. Two pets inside were rescued. Firefighters were on the scene for about two-to three-hours.