The NHTSA's decision whether to investigate was delayed, as the fire happened on the first day of the US government shutdown. AN reports that as of October 22, the administration was still "gathering data," according to a statement by Administrator David Strickland.
The October 1 fire that torched the critically acclaimed EV was started after an impact with a "large metallic object," according to multiple sources including the driver/owner. As we reported on October 3, despite the car-destroying blaze, Tesla maintained that the battery pack acted exactly as designed, by containing the blaze to just one of the battery pack's 16 modules, rather than sending the whole lithium-ion unit up in flames.
Following the fire, Tesla went on a PR offensive with CEO Elon Musk claiming, "You are five times more likely to experience a fire in a conventional gasoline car than a Tesla!" In a report just days after the incident, the company said the fire was started by "a highly unlikely occurrence." The owner of the cooked Model S (and an investor in the company), meanwhile, said he remains a fan of the car.