Fire Capt. Steve Ruda says the blaze began just before 8 p.m. Tuesday and engulfed two football field-sized lumberyards in Pacoima.
More than 100 firefighters were able to save three structures at the site as well as some construction equipment.
No injuries were reported and the cause of the blaze is under investigation.
Although flames have been knocked down, a 70-foot-tall silo laden with sawdust continues to smolder.
Train service on nearby tracks was suspended because firefighters had hoses crossing the tracks. Train service has since resumed.