Forty Los Angeles firefighters knocked down a challenging fire in a commercial building in Van Nuys on Monday. 

Around 6:28 p.m., fire crews responded to a heavy fire inside a one-story commercial building at 14735 West Bessemer Street that housed an upholstery shop and an auto body shop, according to an L.A. Fire Department release. 

Authorities say fire crews “overcame forcible entry challenges, both on the exterior and encountering additional security measures inside, to gain access for hose lines to advance, as other crews ascended ladders to the roof to provide vertical ventilation.” 

40 firefighters helped to extinguish the flames in less than 30 minutes. 

The cause of the fire is still under investigation. No injuries have been reported.