Tesla Motors is defending itself against new allegations that its Model S electric car and charging system caused a fire in Southern California last month.

A fire department in the area said Wednesday that the Nov. 15 fire in Irvine, Calif. may have been the cause of an overheated Tesla charging system, according to Reuters. The fire department’s report noted that the cause was still unclear but that “the most probable cause” was an issue with the electric car.

Steve Concialdi, a spokesperson for the Orange County Fire Authority, told Bloomberg that investigators couldn’t determine if the socket or the charger caused the fire. When a fire involves a wall socket, he said, it’s difficult to determine whether the issue was faulty wiring. Regardless, he added that that the car battery was not involved.

Tesla cars are already under review in connection to battery-related fires, but the company maintains that the Model S had nothing to do with this incident. Representatives pointed out that the fire was based at the wall socket where the vehicle was plugged in and didn’t involve the car itself.

The cable was fine on the vehicle side; the damage was on the wall side,” Tesla said in an email to Bloomberg. “Our inspection of the car and the battery made clear that neither were the source” of the fire.

Concialdi said the Orange County Fire Authority has completed its review of the situation. Now, he said, final determinations of the cause will be left to Tesla and insurance companies.

Despite Tesla’s best efforts to defend itself, it’s still taking hits for fire investigations. Three road fires in the Model S occurred in October and November alone, resulting from collisions that damaged the batteries’ casing. No one was hurt in any of those fires.

Stocks have plunged because of the incidents. Tesla share prices are down about 23 percent from their peak in September.