A Tesla Model S electric automobile, a model which recently won Consumer Reports' Top Scoring Car award and aced the NHTSA's crash rating system, caught fire yesterday in an incident near Seattle. Tesla's shares fell 6.2 percent on the day as a result of the incident.

"Yesterday, a Model S collided with a large metallic object in the middle of the road, causing significant damage to the vehicle," Tesla said in a statement to Jalopnik. "The car’s alert system signaled a problem and instructed the driver to pull over safely, which he did. No one was injured, and the sole occupant had sufficient time to exit the vehicle safely and call the authorities. Subsequently, a fire caused by the substantial damage sustained during the collision was contained to the front of the vehicle thanks to the design and construction of the vehicle and battery pack. All indications are that the fire never entered the interior cabin of the car. It was extinguished on-site by the fire department."

The 85 kWh lithium ion battery is located under the floor of the passenger compartment of the Model S. Only one of the 16 modules was damaged when a metallic object was thrown up from the road and impacted the battery pack. There were no injuries in the fire, which was tackled by firefighters from the Kent Regional Fire Authority. This video, taken by a passer by, shows the fire.

International Business Times relates that, based on an incident report filed by the Regional Fire Authority of Kent, Washington, the fire appeared at one time to be brought under control, but the flames reignited. As water seemed to intensify the fire, firefighters began to use a dry chemical extinguisher. In the end, the front end of the car had to be disassembled. Holes were punched in the battery pack, and a circular saw provided access to apply water to the battery, which finally quenched the fire.

The US government is not investigating the incident, as it has shut down nonessential operations.

UPDATE, October 4, 2013:

Tesla has released the following statement regarding the incident:

About the Model S fire

By Elon Musk, Chairman, Product Architect & CEO

Earlier this week, a Model S traveling at highway speed struck a large metal object, causing significant damage to the vehicle. A curved section that fell off a semi-trailer was recovered from the roadway near where the accident occurred and, according to the road crew that was on the scene, appears to be the culprit. The geometry of the object caused a powerful lever action as it went under the car, punching upward and impaling the Model S with a peak force on the order of 25 tons. Only a force of this magnitude would be strong enough to punch a 3 inch diameter hole through the quarter inch armor plate protecting the base of the vehicle.

The Model S owner was nonetheless able to exit the highway as instructed by the onboard alert system, bring the car to a stop and depart the vehicle without injury. A fire caused by the impact began in the front battery module – the battery pack has a total of 16 modules – but was contained to the front section of the car by internal firewalls within the pack. Vents built into the battery pack directed the flames down towards the road and away from the vehicle.

When the fire department arrived, they observed standard procedure, which was to gain access to the source of the fire by puncturing holes in the top of the battery's protective metal plate and applying water. For the Model S lithium-ion battery, it was correct to apply water (vs. dry chemical extinguisher), but not to puncture the metal firewall, as the newly created holes allowed the flames to then vent upwards into the front trunk section of the Model S. Nonetheless, a combination of water followed by dry chemical extinguisher quickly brought the fire to an end.

It is important to note that the fire in the battery was contained to a small section near the front by the internal firewalls built into the pack structure. At no point did fire enter the passenger compartment.

Had a conventional gasoline car encountered the same object on the highway, the result could have been far worse. A typical gasoline car only has a thin metal sheet protecting the underbody, leaving it vulnerable to destruction of the fuel supply lines or fuel tank, which causes a pool of gasoline to form and often burn the entire car to the ground. In contrast, the combustion energy of our battery pack is only about 10% of the energy contained in a gasoline tank and is divided into 16 modules with firewalls in between. As a consequence, the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan.

The nationwide driving statistics make this very clear: there are 150,000 car fires per year according to the National Fire Protection Association, and Americans drive about 3 trillion miles per year according to the Department of Transportation. That equates to 1 vehicle fire for every 20 million miles driven, compared to 1 fire in over 100 million miles for Tesla. This means you are 5 times more likely to experience a fire in a conventional gasoline car than a Tesla!

For consumers concerned about fire risk, there should be absolutely zero doubt that it is safer to power a car with a battery than a large tank of highly flammable liquid.

— Elon

Sources: Jalopnik, International Business Times