Tesla shares plummeted after a video of a Model S fire was posted online. Officials said the fire originated in the vehicle's battery pack.SEATTLE, Washington - A fire that destroyed a Tesla electric car near Seattle began in the vehicle's battery pack, officials said, creating challenges for firefighters attempting to put out the flames.Tesla's spokesperson Liz Jarvis-Shean said the blaze was caused by a large metallic object that hit one of the battery pack's modules in the Model S. She said the fire was contained to a small section at the front of the vehicle and that no one was injured.Watch the videoShares of Tesla Motors fell more than 6% after a video showed flames spewing from the vehicle, which Tesla has touted as the "safest car in America."Shares of Tesla have risen more than 400% in 2013 but some investors likely were alarmed that the fire could be an indication of a flaw in the company's battery packs, and Tesla shares fell 6% to R1825.37.The liquid-cooled 85kW/h battery in the Tesla Model S is mounted below the passenger compartment floor and uses lithium-ion chemistry similar to the batteries in laptop computers and mobile phones. Investors and companies have been particularly sensitive to the batteries' fire risks, especially given issues in recent years involving the Chevrolet Volt plug-in hybrid car and Boeing's new 787 plane.In an incident report released under Washington state's public records law, firefighters wrote that they appeared to have the fire under control but the flames reignited. Crews found that water seemed to intensify the fire, so they began using a dry chemical extinguisher.HOT MESSAfter 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.The incident happened as the Tesla's driver was traveling through the Seattle suburb of Kent, said Trooper Chris Webb of the Washington State Patrol. The driver said he believed he had struck some metal debris on the freeway, so he exited the highway and the vehicle became disabled.The driver, who did not return a phone call seeking comment, told authorities he began to smell something burning and then the vehicle caught fire.Tesla said the flames were contained to the front of the R700 000 vehicle due to its design and construction.Jarvis-Shean said: "This was not a spontaneous event. Every indication we have at this point is that the fire was a result of the collision and the damage sustained through that."Webb said: "There was too much damage from the fire to see what damage debris may have caused."