California fire officials said Monday that the two fires about 100 miles (161 kilometers) north of San Francisco were 30 percent contained and have scorched 428 square miles (1,108 square kilometers).
The two fires are burning about 14 miles (22 kilometers) apart and have destroyed 75 homes. Another 9,000 buildings are threatened.
The two fires cover an area larger than a deadly wildfire burning near Redding, California.
That blaze has killed two firefighters and five civilians and destroyed more than 1,000 homes.
The wildfire started two weeks ago by sparks from the steel wheel of a towed-trailer’s flat tire. It is 45 percent contained.