By MIKE BAKER and TOM KRISHERSEATTLE (AP) â¿¿ A fire that destroyed a Tesla electric car near Seattle began in the vehicle's battery pack, officials said Wednesday, creating challenges for firefighters who tried to put out the flames. Company spokeswoman Liz Jarvis-Shean said the fire Tuesday was caused by a large metallic object hitting one of the battery pack's modules in the pricey Model S. The fire was contained to a small section at the front of the vehicle, she said, and no one was injured. Shares of Tesla Motors Inc. fell more than 6 percent Wednesday after an Internet video showed flames spewing from the vehicle, which Tesla has touted as the safest car in America. The liquid-cooled 85 kilowatt-hour 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 Tuesday's fire under control, but 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. The incident happened as the Tesla's driver was traveling southbound on state Route 167 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.