The Mill Fire in Weed (Siskiyou County) has destroyed dozens of homes and vehicles. Investigators are searching for clues to the fire’s origin.

Cal Fire investigators combed through the remains of a lumber mill warehouse and the area nearby on Friday and Saturday, searching for clues as to what sparked the fast-moving blazes that torched dozens of homes in the tiny town of Weed.

The Mill Fire ravaged the massive storage warehouse owned by Roseburg Forest Products on Friday and spread into the Siskiyou County town, where it razed or damaged 50 houses. Officials at Cal Fire have not determined a cause, but firefighters were first dispatched to the Mill Fire as a structure fire at the mill shortly before 1 p.m. Friday.

“We don’t know how or where the fire started,” said Rebecca Taylor, a spokesperson for the Oregon company. “Whether it started right on the edge of the property or on the property.”

The fire completely destroyed the old warehouse where Roseburg stored spare equipment for its veneer mill nearby, she said.

Cal Fire investigators combed through the remains of Roseburg Forest Products’ storage warehouse in Weed (Siskiyou County) for clues to the origin of the Mill Fire.

“We weren’t doing any work around that building at the time,” Taylor said. “Every once in awhile we might go into that building to get spare parts, but that’s it.”

On Friday, at about 12:48 p.m., firefighters reported seeing black smoke billowing “at the mill,” according to radio traffic reviewed by The Chronicle. A Weed City Fire Department station is next door to the massive Roseburg property.

Immediately multiple alarms were sounded for a “fully involved commercial structure fire,” according to the initial dispatch response. The first firefighters at the scene estimated the building to be about 50,000-square-feet and already flames were jumping Highway 97 with a strong south wind and entering into the Lincoln Heights neighborhood. On Saturday, that rural community was still smoldering, blackened with charred cars and gray lots where houses once stood.

Roseburg bought the sprawling operation in 1982 from International Paper. The warehouse used to house a planer mill that would cut and season wood to create lumber products. In recent years, the building mostly stored spare parts from the active veneer mill.

The veneer mill was operating when the fire began and it was not touched by the flames, Taylor said. Workers assigned to the afternoon shift were evacuated as the flames whipped by. A small fire patrol crew stayed behind to protect the rest of the plant from fire.

The veneer mill spins logs and peels off thin strips used to press together for plywood. Those veneers are shipped to Oregon where the company has plywood factories. The mill has a cogeneration plant which helps dry the wood strips, Taylor said.

“None of the equipment from the veneer operations were involved in the fire,” she said.

Since the fire, Cal Fire investigators have visited the plant and nearby properties, Taylor said. A Cal Fire spokesperson could not be reached Saturday evening.

The Weed plant has 145 workers, making it a massive employer for the tiny town. Taylor said she confirmed that at least two employees lost their homes in the fire Friday.

“It’s truly devastating that it’s happened in Weed again,” Taylor said.

In 2014, the Boles Fire caused major damage at the plant. A homeless man was convicted for starting that blaze when a warming fire got out of control and burned more than 150 buildings in the Weed area. Following the fire, Roseburg moved many of its Weed employees to Oregon to work for their facilities there as they rebuilt the plant and workers’ lost homes.

Matthias Gafni is a San Francisco Chronicle staff writer. Email: matthias.gafni@sfchronicle.com

Matthias Gafni is an enterprise reporter for The San Francisco Chronicle. He investigates stories in the East Bay and beyond. For almost two decades, Gafni worked for the Bay Area News Group - San Jose Mercury News, East Bay Times and Vallejo Times-Herald - covering corruption, child sexual abuse, criminal justice, aviation and more. In 2017, Gafni won a Pulitzer Prize for breaking news for his work on the Ghost Ship fire. In 2018, he was named SPJ Reporter of the Year in Northern California. The following year, he was a finalist for a Pulitzer Prize for breaking news for his work covering the Camp Fire. In 2020, he won a Polk Award for military reporting for his coverage of the Capt. Crozier saga involving a COVID-19 outbreak aboard a U.S. aircraft carrier. He was born and raised in the Bay Area and graduated from UC Davis. He lives with his wife and three kids in the East Bay.