At 1:30 PM Wednesday LAFD responded to a reported structure fire at 8560 Tunjunga Ave. First arriving companies reported smoke showing from a one story commercial building. Firefighters were meet were meet with a well secured building making entering the building difficult. Once inside firefighters found a fire being held in check by a sprinkler system. A “large” marijuana grow operation was discovered during the course of the fire. LAFD firefighters were able to achieve a knock down in roughly twenty minutes. The cause of the fire is unknown at this time, and firefighters requested arson and LAPD to the location.