At 0125hrs on Sunday 2/19, Tower 18 and Deputy 18 responded to assist Christiana Fire Company on a Residential Fire in the unit block of Lake Drive in the Crofton Community. First arriving units from Christiana reported smoke showing. Tower 18 arrived as the third due special service and fulfilled the RIT role. During the fire, crews reported a basement fire and a spongy floor on the 1st floor. Crews were removed from the structure by Command and a collapse occurred shortly after all crews had exited. A switch to a defensive operation was made and Tower 18 was reassigned to place the aerial in service. Tower and Deputy 18 operated for approximately 3 hours before being cleared.