It's been burning since Tuesday afternoon near Oroville north of Sacramento and has destroyed at least ten homes and 20 other buildings.
Cal fire investigators say they arrested a man from Oroville who they believe ignited the fire.
They say he recklessly started an illegal campfire.
Flames have scorched nearly 4-square-miles and threatened 500 structures.
There are currently two evacuation centers for residents under an evacuation warning.