At 0125 hours, Station 58 was alerted for the Truck to respond to a 59 box for a possible chimney fire. Truck 58 went enroute with three (3) and Car 58 responded with additional manpower. While enroute, Command advised of a working chimney fire with extension. Upon arrival, Command had the Truck ladder the roof and check the chimney. The Truck crew checked and found nothing. The crew staged and then assisted Station 59 with overhaul. Command placed the box in service at 0320.