At Approximately 0536hrs Station 93 was dispatched for the smoke investigation in the area of Maple Ave.  While investigating, Chief 93 arrived on-scene and reported the working structure fire and upgraded the alarm to a structure box.  Crews encountered heavy fire and were forced to operate defensively. The fire was soon upgraded to a second alarm.  Ladder 4 arrived on-scene and was assigned to the “B-C” corner, division 1.  After completing overhaul, the crew was reassigned to side “A” for additional overhaul.  Once complete, Ladder 4 was released by command and returned to service.  Crews remained on-scene for several hours.