Some structures may be threatened by the flames.
The Route Fire was reported just before 4 p.m. along the 5 Freeway near Templin Highway.
The CHP closed the southbound 5 at Vista del Lago Road and the northbound 5 at Templin Highway.
The fire was first estimated at 5 acres but spread to at least 50 in less than two hours.
DEVELOPING: This story will be updated.