The fire was reported around 9:25 a.m. at 200 Morris St., a former apple processing plant known as The Barlow, Assistant Sebastopol Fire Chief Mike Reeser said.
The blaze was burning about half of the 30,000-square-foot metal building, which now holds vintage clothing for the Aubergine clothing company, Reeser said. The clothing was bundled and stored on pallets in half of the warehouse to be shipped to retail outlets, he said.
The other half of the warehouse is not on fire and no one was in the warehouse when it caught fire, Reeser said.
Firefighters from Sebastopol, Santa Rosa, Gold Ridge and Graton tore down the sheet metal to get to the burning clothing inside. Overhaul operations at the building are expected to continue until the late afternoon or evening, Reeser said.
A preliminary cause of the fire is construction activity that might have involved a welding torch at the warehouse, Reeser said.