The fire was reported at 7:45 a.m. at the Padula Lumber Co. at 8149 Monterey Road, just outside of San Jose city limits.
As of 9:15 a.m., the blaze had been contained and had not spread beyond the yard, but the lumber company's main building had collapsed and other buildings were burning, Cal Fire Capt. Paul Provence said.
No injuries have been reported, he said.