By TOM KRISHERDETROIT (AP) a¿¿ U.S. auto safety regulators have decided not to open a formal investigation into the Oct. 2 fire that damaged a Tesla electric car near Seattle. The National Highway Traffic Safety Administration said Thursday there's no indication at this time that the fire was caused by a safety defect or that there was any violation of federal vehicle safety standards. The agency said in a statement that it reviewed all available data and will continue to check consumer complaints and other information. A NHTSA spokesman said that he could not comment beyond the statement. The Tesla Model S hit road debris on a freeway in Kent, Wash. The debris punctured an underbody shield and the battery, which is mounted beneath the passenger compartment. The crash touched off a fire that engulfed the front of the car. The driver escaped without injury and firefighters put out the flames. Experts say when a battery cell is pierced, it can cause a short circuit that can lead to arcing and sparks that can touch off a fire. The fire happened during the 16-day partial government shutdown earlier this month, delaying NHTSA's response. Normally the agency would send investigative teams to such an event shortly after it happens. The fire became an Internet sensation when witnesses posted a video of it. The stock of Tesla Motors Inc., which is based in Palo Alto, Calif., tumbled as word of the fire spread. Tesla CEO Elon Musk said the car, which starts at $70,000, apparently was impaled by a metal object. Musk, in a blog post, defended the car's battery technology and said fires are more common in conventional gas-powered vehicles. The CEO said a curved metal object on the road was apparently to blame. The large 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 battery.