A car fire destroyed a Gorham carwash and caused extensive damage to an adjacent convenience store late Friday afternoon.

The three-alarm fire started about 4:15 p.m. at 601 Main St., also known as Route 25, at the TNT Quick Stop gas station, carwash and convenience store. No one was injured.

The fire closed down Route 25 between Bartlett and Mosher streets until shortly after 5 p.m., and at least five fire departments were on the scene. The fire was extinguished by 6 p.m.

Robert Lefebvre, chief of Gorham Fire & Rescue, said the probable cause was an electrical short-circuit in the dashboard of a car that was being washed at the time.

“The vehicles today are made of a lot of plastic,” Lefebvre said, “and plastic, when it heats, it returns to its natural form, which is oil. It doesn’t take much. Once you get any type of fire at all and it starts burning the plastic, it’s an oil fire. The plastic just feeds it, and it only takes a couple or three minutes for it to really get going.”

The fire spread from the car wash into the ceiling space of the convenience store, where there was a lot of smoke and water damage, Lefebvre said.

“A quarter of the roof of the store has collapsed,” he said. “A lot of their machinery and stuff like that is probably salvageable. I’m not sure if the store itself will be declared a total loss or not, but they’ve got extensive damage.”