The fire department first received reports of the blaze at the warehouse at 19600 Almaden Road around 3:55 a.m., the dispatcher said. The warehouse is home to Almaden Valley Gymnastics.
Fire crews en route to the fire upgraded the incident to a 2-alarm fire after spotting heavy smoke and later to a third alarm after encountering heavy fire at the scene, according to the dispatcher.
As of 6 a.m., the fire was about 90 percent contained, and no injuries had been reported.
