House fire reported in the 20900 block of Twin Springs Drive in Chewsville. Co 9, 7, 10, Tankers 9, 7, 16, Quint 27, Rescue Squad 75 and Medic 75 were alerted. Assistant Chief 79 arrived on the scene advising light smoke condition throughout the house. Chief 75 on the scene assumed Command until the arrival of Chief 9, Capt. 75 had Operations. Engine 71 arrived and laid LDH from the hydrant with Engine Tanker 7 picking up the plug. Engine 92, Chief 9 arrived on the scene and Command was transferred from Chief 75. Quint 27 took position on side Alpha and prepared to ladder the roof. Crews conducted extensive investigation of the source of the smoke. The furnace was shut down immediately on arrival of units and the smoke began to clear. Crews investigated throughout the residence with thermal imagers and meters and found no apparent fire. Command had crews re-energize the furnace to determine whether this was the source. Furnace ran for a period of time and did not seem to malfunction. Command placed the units in service on apparent furnace malfunction. Units cleared at approximately 0100.