Crews were called to Shaw and First at around 11:30 Tuesday night.
Helmet cam video shows flames tearing through the vacant building that once housed local radio stations including KRZR, B-95, KCBL and New Rock 104.
Fresno Fire Public Information Officer Shane Brown says, "Conditions reached a point called 'flash-over,' where everything within the structure reaches a temperature where everything in the building starts to catch on fire."
He says the initial call to 911 suggested the fire was small, but when crews arrived, flames had quickly erupted.
Brown says, "At that point, there was no controlling it, there was no stopping it, so it was just protect everything else around it."
Over 30 firefighters kept flames from reaching neighboring businesses and homes. But like most of the city's vacant structures, this wasn't the first time crews were called to the property on Shaw and First.
Brown says, "They've had fires on the exterior because of homeless activity before. The crews are aware of that, so we look at these vacant buildings with a different eye."
Vacant structures pose a threat across the City of Fresno.
Of the more than 600 structure fires crews have faced off against, since January 1, more than 10% were vacant.
In addition to fire crews identifying vacant structures across their shifts, city council now passed a new law holding vacant commercial property owners liable for fires.
Councilman Miguel Arias says they've seen a growing demand from out-of-town investors for Fresno's commercial property.
The law, passed unanimously, requires owners to secure vacant buildings from trespassers and install fire sprinklers.
Arias says, "We're getting a good response from our property owners. They're realizing it's not going to be cheap to keep your building boarded up, non-secure, not being checked on."
Per the city, debris from Tuesday's fire will be removed within the next 30 days at the property owner's expense.