A fire that ignited a Tesla Model S sedan in the state of Washington earlier this month was started in the vehicle’s battery pack, which was pierced by a metal object on the road, says company CEO Elon Musk.

According to Washington State Patrol Trooper Chris Web, the crash took place on October 1 in the city of Kent at approximately 8 a.m., where the driver of a silver Model S said he thought he had struck a piece of metal debris on the road. He exited the freeway as a precaution, at which time the vehicle became disabled. He then reported a burning smell coming from the vehicle, which caught fire soon thereafter. Firefighters were quickly called to the scene to put out the blaze, which required several attempts, as the fire repeatedly reignited.

To fully extinguish the flames, firefighters had to dismantle the front end of the vehicle, puncture holes in the battery pack, and use a circular saw to cut an access hole in the pack’s front section to apply water directly to the battery.

In the aftermath of the incident, state troopers were unable to locate any metal objects in the road that the vehicle may have driven over, but crews from the Department of Transportation did report debris near the scene.

Photos and video of the burning vehicle were quickly posted online, igniting safety concerns over the all-electric vehicle. Tesla’s stock price fell sharply in response, down $12.05 in a single day, the largest drop in more than three months. Musk was quick to defend the safety of the Model S however, noting in a blog post on his website that fires are much more common in gasoline powered vehicles. “For consumers concerned about fire risk, there should be absolutely zero doubt that it is safer to power a car with a batter than a large tank of highly flammable liquid.”

The cause of the fire, says Musk, was a curved metal object that punched a three inch hole through an armored plate protecting the undercarriage of the vehicle and into one of the battery pack’s modules, causing a disruption in the electrical current. As the fire ignited, he added, the vehicle contained the flames to the front of the vehicle as intended. “This was not a spontaneous event,” said Tesla spokesperson Liz Jarvis-Shean. “Every indication we have at this point is that the fire was a result of the collision and the damage sustained through that.”

The threat of fire in electric vehicles has long drawn concern from the car buying public, though much of the fear may be overblown. In 2011, three Chevrolet Volt plug-in hybrid vehicles caught fire during federal testing, but an investigation by the National Highway Traffic Safety Administration revealed that the vehicles were no more dangerous than gasoline powered vehicles. Nevertheless, the Volt’s reputation suffered greatly, and sales dropped considerably.

Tesla and Elon Musk are hoping to avoid a similar fate with the Model S, which is already being called “the safest car in America” after receiving a near perfect crash test rating from the NHTSA, and the highest test score ever recorded by Consumer Reports magazine. The car is powered by a liquid-cooled 85 kilowatt-hour battery mounted underneath the passenger compartment floor made from lithium-ion similar to the batteries found in cellphones and laptops, and it can be powered through any standard 240-watt outlet. With a full charge, the Model S can cover as many as three hundred miles.