I remember reading somewhere saying that the possible cause of fire is sea water gets into the electrical system. After some time, the salt corrosion inside the electrical system caused a short circuit then the fire.
http://www.edmunds.com/car-news/fisker-reveals-cause-of-karma-fires-during-hurricane-sandy.html
"After a thorough inspection witnessed by (National Highway Traffic Safety Administration) representatives, Fisker engineers determined that the damage to the Karmas was the result of the cars being submerged under 5-8 feet of seawater for several hours that left corrosive salt in a low-voltage Vehicle Control Unit in one Karma," the company said.