Update 10 p.m.
Cal Fire reported the fire grew to 5,000 acres and was 60 percent contained late Friday evening.
A fire likely sparked by a training exercise at a Camp Roberts rifle range has burned 500 acres and is making for smoky driving on nearby Highway 101.
Cal Fire reported the fire in a tweet about 2:15 p.m., and a dispatcher said it was about 30 percent contained. Motorists driving in the area should use caution, as smoke can be seen from the roadway, Cal Fire said.
Capt. Jason Sweeney, a Camp Roberts spokesman, said the fire started on the range in the northeast corner of the base, near Highway 101 and a rest stop. Troops training in the area were firing rifles, which probably caused the fire, he said.
The base had been set to conduct a controlled burn Thursday on the range where the fire started, to prevent just such incidents, Sweeney said. No injuries or structural damage were reported.