At 13:18hrs Truck 21 was sent on the MCFRS box for the reported structure fire in the 5100 block of Fountainbrook. With Battalion 31 advising of a column from a distance, on arrival smoke was reported from Side C of a 2-story SFD. Upon arrival of Truck 21 personnel initiated searches while the aerial was placed to the A/D corner roof. With the fire in the rear 1st floor addition quickly knocked down by Ladder 31 and searches negative, personnel shortly thereafter found evidence of a potential grow house operation. With all personnel withdrawn from the structure, and the scene held for investigators and law enforcement, Truck 21 returned to service. During the incident 2104 was assigned as the Incident Safety Officer.