In the early morning hours of August 20, 2009, Companies 1, 7, 6, Truck 1, Water Supply 5 and Amb. 196 were dispatched to 21500 Abells Wharf Rd. in Medleys Neck for a reported working house fire with possible subjects trapped. Chief 1 (Trossbach) responded shortly after dispatch and arrived on the scene with a 2 story multii family dwelling with fire showing from side A from a 1 story addition. Engine 10 with Chief 1A (Mattingly) responded with 4 personnel. Upon arrival of Engine 10, Chief 1 was able to verify that all occupants had evacuated the structure and uninjured. Engine 10 layed out from the driveway and Engines 14 and 74 supplied Engine 10. Truck 1 was assigned to side A and started ventilation and laddering of the structure. The crew from Engine 10 started the fire attack. Shortly after while trying to advance the line into the attic area, the first floor ceiling collapsed on the crew. All crew members were uninjured and able to evacuate the structure. Shortly after this collapse the entire roof of the addition to the residence collapsed. Crews from Engines 73, 74, and 63 checked the primary structure for extension, conducted searches, and assisted with ventilation and extinguishment of the fire. Water Supply set up a fill site at the dry hydrant at Maryland Rock. The fire was brought under control after about an hour. The state fire marshal's office was called in to investigate the incident and the cause of the fire was attributed to a pump for an aquarium that had malfunctioned. Damage is estimated to be approximately $175,000. The incident was under command of Chief 1. Units returned to service at 0607 hours.