An industrial fire destroyed three businesses in North Hollywood on Friday before being extinguished by firefighters early Saturday morning.

The blaze started at Auto Giant Supplies at 6836 Lankershim Blvd., near Vanowen Street, at around 11:30 Friday night. It quickly grew to engulf the whole 10,000-plus-square-foot facility, then spread to neighboring businesses, including a film set design studio and an art supply warehouse, both of which contained highly flammable materials. Flames leapt above the roofs for more than three hours before a team of more than 120 firefighters drowned the fire Saturday morning.

The fire also knocked out power to most of Lankershim Boulevard’s 6800 block.

After reviewing security camera footage, the Los Angeles Fire Department arson unit determined the fire was caused accidentally when a pile of oily rags spontaneously combusted due to a chemical reaction.

“This is a sobering reminder to properly dispose of oily and chemical-soaked rags properly,” said LAFD spokesperson Nicholas Prange in a statement released Sunday.

No injuries were reported.