SEATTLE -- The CEO of electric car company Tesla says a battery in a Model S that caught fire this week was apparently impaled by a metal object.
Elon Musk gave more detail in a blog post Friday about the fire that became an Internet sensation and unsettled Tesla investors. He also defended the car's battery technology.
Musk wrote in a blog post Friday that fires are more common in conventional gas-powered vehicles.
"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," Musk wrote.
The CEO said a curved metal component was apparently the culprit in causing a Tesla to catch on fire Tuesday. He says the object's shape led to a powerful hit on the underside of the vehicle, punching a 3-inch hole through an armor plate that protects the car's bottom.
The company said the car properly contained the blaze. The driver was able to exit the highway in the Seattle suburb of Kent before flames engulfed the front of the vehicle.
Of the estimated 194,000 vehicle fires in the U.S. each year, the vast majority are in cars and trucks with gasoline or diesel engines. Electric vehicles make up less than 1 percent of the cars sold in the U.S.
Firefighters struggled to extinguish the Tesla fire, finding that the flames reignited. Crews found that water seemed to intensify the fire, so they began using a dry chemical extinguisher.
After dismantling the front end of the vehicle and puncturing holes in the battery pack, responders used a circular saw to cut an access hole in the front section to apply water to the battery, according to documents. Only then was the fire extinguished.
Tesla shares fell sharply Wednesday and Thursday after a video of the car fire circulated on the Internet. The shares recovered somewhat Friday, rising $7.67, or 4.4 percent, to $180.98. They still finished the week with a loss of $9.92, or 5.2 percent. The shares are still up more about 400 percent.