It happened around 1 a.m. at the Pendergrass Flea Market in Jackson County.
The flea market manager said 60 stores in the flea market were completely destroyed by the fire.
Investigators said one of the buildings, about 25,000 square feet, was completely destroyed.
Fire Destroys Flea Market
Firefighters said the heat was so intense it caused the metal roof of the building to collapse on itself.
Firefighters are expected to remain at the scene throughout the day to control any hot spots.
No one was injured in the fire, according to firefighters.
Fire investigators are still trying to determine what caused the fire.