The blaze was reported shortly after 10:30 p.m. at a commercial structure in the area of Grand and Santa Anita avenues. There were no immediate reports of injuries.
The building’s roof collapsed during the stubborn fire, which Los Angeles County Fire Department firefighters doused from atop ladders and on the ground.
The flames, visible from at least 12 miles away at one point, were knocked down within about an hour.
The cause of the incident was not immediately known.