On 12-2 at 1527 hrs. Holbrook was activated for a report of a residential structure fire on Skylark Drive in Holtsville. Being in close proximity to Station 2 Engine 5 was first to arrive at scene and reported a working fire two story residential with heavy fire being observed on both the first and second floors. An aggressive interior attack was made with firefighters finding a heavy load of fire throughout the entire first floor. Mutual aid plan was activated bringing an additional Ladder and a Rapid Intervention Team to the scene. Reports were made of two 100 lb. propane tanks that had already been compromised and were bleeding off and ignited on the number 2 side. Additional lines had to be stretched to address this issue as the interior lines continued their attack to both the first and second floors. Units were on scene for approximately 2 1/2 hours due to the extensive overhaul that had to be done. Suffolk County Arson squad and Town of Islip Fire Marshal are investigating.