Officials believe the fire may have been burning all day, but very little smoke was visible from the outside because of the size and design of the building. It is also an old building, which created even more safety concerns.
"These hallways are full of holes, collapsed walls, collapsed ceilings can't see or feel anything, rely on senses," Tony Escobedo said.
Firefighters used thermal imaging cameras to help them pinpoint the source of the fire on the second story. They also had a rescue team on standby just in case anyone got trapped inside the building. No one was hurt, and investigators are still looking into what caused the fire.