Santa Maria crews responded Wednesday night to a fire alarm at a commercial structure at 619 S. Oakley Ave.
Battalion chief Rick Bertram said units arrived about 8:30 p.m. and found light smoke and embers emitting from around a roll-up door of a single-story multiunit commercial structure.
The captain called for a full structure response, brining in three additional units and a battalion chief.
Bertram said the fire started in oak wine barrel material and a large pile of rags.
Crews opened the roof to ventilate and extinguished the fire.
Damage was estimated at $30,000, and the cause of the fire is under investigation.