A dark plume was clearly visible around southwest Santa Rosa on Saturday afternoon after a fire broke out at a large industrial building and destroyed at least two businesses, fire officials said.

Around 2:23 p.m., firefighters arrived at a building near the 300 block of West Robles Avenue, between Moorland and Standish avenues, for a fire that began in a building that houses plumbing, heating, metal fabrication and woodwork businesses.

Across the parking lot from the building, Jorge Gutierrez, 29, owner of Hexa Motorsports, was alone in his shop when he heard multiple explosions and loud popping sounds.

“I couldn’t make it out through the front because cars were catching on fire,” said Gutierrez. “It was huge, the building was up in flames.”

The fire spread to about half an acre of nearby vegetation and was contained by 3:12 p.m., according to Rincon Valley-Windsor Fire Battalion Chief Aron Levin.

Gutierrez’s Lexus was parked in the lot between the building and his shop, and he said the fire damaged it beyond repair.

“It looks like a lump of plastic,” Gutierrez said.

One of the businesses lost was Bavarian Timberwork, a custom timber design and construction business founded about 15 years ago by German immigrant Gerhard Gassner, 56.

For the last two years, Gassner had rented Unit L at one end of the building. He left his 3,000-square-foot work space at 11 a.m. to go to a job site, and came back in the afternoon to find it in ruins.

He lost expensive, specialized German tools for timber framing, an old-fashioned method of wood construction he said is similar to Amish woodwork.

“My life is gone,” Gassner said. “It’s very difficult to replace my tools.”

Levin said the cause of the fire is still under investigation, and the amount of damage was yet to be determined.

A Rincon Valley firefighter sustained minor burns that were treated at the scene, Levin said.

Multiple fire agencies responded to the brush and building fire, including Rincon Valley, Santa Rosa, Healdsburg, Sebastopol and Monte Rio.

You can reach Staff Writer Susan Minichiello at 707-521-5216 or susan.minichiello@pressdemocrat.com. On Twitter @susanmini.