They poured water on the building from a couple of ladder trucks for more than two hours, starting just after 5 a.m., but the flames basically destroyed the building.
Firefighters called out two alarms as they tried to keep those flames from jumping to nearby buildings and the train tracks just to the south.
Investigators found several mattresses sitting just outside and the building had a lot of fuel to burn.
"That fire burned quick and fast," said Fresno firefighter Rob Castillo. "The building is currently being used to store furniture and mattresses so you can imagine how hot that fire burned."
Firefighters say nobody was in the building by the time they got there and they don't have any clues yet about how it started.