At 01:00 Hours, Station 38 & mutual aide were dispatched to the 3300 Block of Walnut Street for a reported house fire. Chief 38 arrived to a 2-story twin with nothing showing side Alpha, Bravo, & Delta. Engine 38 arrived as the first due engine; crews stretched a line & began investigating. The source was determined to be a discarded cigarette, and the incident was scaled back to 2&1.