On February 4th at 01:44, Aetna was dispatched for an Engine and Ladder to assist Christiana Fire Company on a working building fire at 49 Cheswold Boulevard.  Squirt 7 and Ladder 9 both made the response.  While units were responding, Fire Board advised that New Castle County Police were on scene reporting smoke showing and possibility of a subject trapped.  Command 12 was first to arrive at 01:50 and confirmed the report of a working fire.  Ladder 9 arrived at 01:55 and positioned on the C side of the building.  The aerial was placed to the roof while the crew threw multiple ground ladders on the C side.  The crew then reported to the interior to assist with search operations.  Squrt 7 arrived at 01:56 with the crew first being tasked to secure the hydrant line for Engine 3-6.  The crew then reported to the A side of the structure where they were placed in service on the first floor.  The crew went to the fire apartment and assisted with opening the walls and ceiling.  The crew found fire extension through the ceiling into the neighboring apartment.  The hose team was advised and Squrt 7's crew opened up the ceiling so that extinguishment could be completed.  Command placed the incident under control at 02:27, with Aetna units operating until they were released.  Squrt 7 cleared at 02:45 and Ladder 9 cleared at 03:38.