By contrast, the arsonist behind the Napa fire was given 27 years in prison last year.
Local media had been reporting that the arsonist was using some kind of Molotov cocktail to smash through the car windows.
But fire department officials are not saying what they suspect the arsonist is using to ignite the fires.
Even so, police and fire officials say they are not sure if they are dealing with one arsonist or many.
But fire-department officials are not saying what they suspect the arsonist is using to ignite the fires.
