The fire happened at what is now Cal-Tex Industries on Beaumont Highway. The building used to be a paper mill and it was just sold last week, officials said. It was supposed to be changing hands Tuesday.
Firefighters arrived around 11pm Monday to find heavy flames shooting from the second floor.
Six fire departments battled the flames.
It's not clear what sparked the fire, but security guards say copper thefts have been an issue at the warehouse. They believe a thief was at the facility moments before the fire started.
A crane operator died in January 2009 at that same location when a 6-foot wall collapsed during demolition.
No one was hurt during last night's fire. It remains under investigation.