Kittitas County Fire and Rescue spokeswoman Richelle Risdon told KIRO-TV, Seattle, that the Taylor Bridge fire had destroyed 60 homes since it started near Cle Ellum.
The fire was already 12 miles long by Monday evening and had jumped U.S. Highway 97, forcing the state Transportation Department to close the road between Milepost 147 and Milepost 149.
More than 150 firefighters from across the region were fighting the blaze with additional personnel on the way, the Yakima Herald-Tribune reported.
Three helicopters and two fixed-wing airplanes were dropping fire retardant.
Ellensburg, located just east of the Cascade mountain range on Interstate 90, is the most centrally located city in Washington state.
The Taylor Bridge fire is just one of 16 fires raging across California, Oregon, Nevada, Washington and Idaho.