Two people are being treated for smoke inhalation after fire tore through a mill in the North Okanagan.

The blaze broke out at the wood re-manufacturing facility, located east of Vernon and the district of Coldstream along Highway 6, just after 9 a.m. PT Tuesday morning.

Witnesses say the fire was so intense it melted the sides of adjacent buildings on the property and that firefighters had to take water breaks to get away from the extreme heat.

Flames rip through Coldstream Lumber in the Okanagan.

One person was taken to hospital for treatment for smoke inhalation from the fire at Coldstream Lumber. (Photo courtesy Dave Dunnink)

Dave Dunnink works at Burnco Rock Products, just across the road from the mill, and says flames were shooting 20 feet into the air.

"I was in the loader and I seen just piles of smoke coming out of there and I thought, that's not normal, right? And then it wasn't even five minutes later you could see the flames coming through the roof," Dunnink told CBC News.

"I didn't hear any explosions, about the only thing I heard was popping and that was the transformers," he said.

Witnesses say the fire started in two kilns used to dry lumber for custom work and other products.

The fire was under control by the afternoon. The cause is under investigation.

"The building is an absolute write off," said Chief Shane Code of the Coldstream fire department. "Investigators are on the scene now and we'll be working to figure out what the root case was."

Coldstream Lumber has operated out of the same location for the past 58 years.

With files from the CBC's Luke Brocki