(Portland, OR) -- An arson investigation is ongoing into a fire that destroyed four electric Amazon delivery vans in Portland. It happened early Monday at a Rivian dealership in Southwest Portland. Firefighters responded to a report of trees on fire and found four of the vans were burning. Batteries in electric vehicles burn extremely hot, and once they start burning, they either have to be drowned with water or allowed to burn out. Firefighters let them burn and kept the flames from spreading. No one was injured in the fire.