The Manton Way fire between Mesa and Connell has grown to 8,700 acres and is now 70% contained, according to Franklin Co. Fire District #1.
Chief Eric Mauseth said crews have been working around the clock since the fire first broke out around 1 p.m. on Monday. Franklin Co., Walla Walla Co., Benton Co., state and federal agencies are all on scene.
The fire started along Hwy 395 and was initially only half an acre. Strong winds caused the blaze to spread over thousands of acres.
Southbound lanes of the road were initially closed when it first broke out. They have since reopened and traffic is flowing normally, although officials are asking drivers to be careful.
No homes have been threatened and all evacuations are voluntarily.
The cause is still under investigation.