The Plumtaw fire north of Pagosa Springs has grown to more than 600 acres and was still zero percent contained, the U.S. Forest Service announced Wednesday.

The agency said the fire had reached Fourmile Road, and firefighters were trying to stop the flames from spreading west of the road. 

Mandatory evacuation orders were in effect for the Lost Valley of the San Juans community in Mineral County. 

Investigators have not determined what caused the fire.