Tesla Model S probed by U.S. after three fires in five weeks

WASHINGTON (Bloomberg) -- Tesla Motors Inc.'s Model S, the plug-in electric sedan marketed by the company as "the safest car in America," is being investigated by U.S. auto regulators in a possible precursor to a recall.

The U.S. National Highway Traffic Safety Administration announced the preliminary evaluation today in a Web site posting, saying it would look into the fire risks from the cars' undercarriages striking objects. The probe involves all 13,108 Model S vehicles, it said.

On Wall Street, news of the investigation -- which followed three fires in five weeks after roadway mishaps -- did not hurt Tesla shares. The stock rose 3.7 percent to close the day at $126.09. Before today, the shares slid 37 percent since reaching a closing peak of $193.37 on Sept. 30, the day before the first fire.

Tesla CEO Elon Musk, who last week said "there's definitely not going to be a recall," said in a blog post hours before the filing that the company sought the probe to counter "false perceptions" about the car's safety.

NHTSA Administrator David Strickland said today that he is "not aware" of Tesla having made such a request. He said NHTSA notified Tesla on Friday that it intended to open a formal investigation.

"In my time as administrator and my time as oversight counsel, I've never heard of an automaker formally requesting an investigation," he said on the sidelines of a U.S. House hearing. "That also has lots of implications. That means that that automaker has some notion, or level of belief, that they have a defect that poses an unreasonable risk to safety … so this [would be] unprecedented, and I don't think this probably happened in this case."

Musk, in a midday tweet, responded by writing Tesla vice president of regulatory affairs, Jim Chen, on Friday "invited NHTSA senior staff to conduct a review of Model S."

In his earlier blog, Musk said Tesla will amend its warranty to cover damage due to fires and update its air suspension to allow greater ground clearance at highway speeds.

"While we think it is highly unlikely, if something is discovered that would result in a material improvement in occupant fire safety, we will immediately apply that change to new cars and offer it as a free retrofit to all existing cars," Musk wrote.

Two of the three fires occurred in the U.S. when cars ran over metal objects, which then punctured the cars' lithium-ion battery packs. A third, which followed a high speed crash, was reported in Mexico on Oct. 18.

Drivers were uninjured in all the fires.

A preliminary investigation is the first step in NHTSA's process that could lead to a recall if regulators determine that a manufacturer needs to address a safety issue. The next stage of the process, if warranted, would be an engineering analysis.

Thermal runaway

In announcing the probe, NHTSA said both U.S. incidents led to thermal runaway, a phenemenon also found in the lithium-ion batteries on Boeing 787 Dreamliner airplanes that led to the plane's grounding earlier this year.

NHTSA said Oct. 24 it found no evidence the first fire resulted from defects or violations of U.S. safety standards. It didn't send investigators to the scene of that accident, in Washington state, because it occurred on the initial day of a partial U.S. government shutdown.

Two months earlier, the Model S received the highest possible ratings in NHTSA's crash tests, getting top five-star rating in each category.

NHTSA previously investigated fires in two other electric cars, the hybrid electric General Motors Co.'s Chevrolet Volt and Fisker Automotive Inc.'s Karma plug-in. The Karma was recalled and GM voluntarily reinforced the battery packs on Volts, after one caught fire days after a NHTSA crash test.

'Larger issue'

California safety officials separately are investigating an industrial accident at Tesla's plant that burned three workers last week.

"Given that the incidence of fires in the Model S is far lower than combustion cars and that there have been no resulting injuries, this did not at first seem like a good use of NHTSA's time compared to the hundreds of gasoline fire deaths per year that warrant their attention," Musk wrote in his blog post.

"However, there is a larger issue at stake: if a false perception about the safety of electric cars is allowed to linger, it will delay the advent of sustainable transport and increase the risk of global climate change, with potentially disastrous consequences worldwide," Musk wrote.

Musk also cited a Nov. 8 blog in Automotive News, noting the low incidence of fires in the Model S compared with gasoline-powered vehicles.

"Why does a Tesla fire w no injury get more media headlines than 100,000 gas car fires that kill 100s of people per year?" Musk tweeted this morning.

Karl Brauer, senior analyst at Kelley Blue Book, said Musk can’t rely on his statements that the Model S catches fire less often than gasoline-powered cars.

“While only three Tesla fires have occurred, that’s three more than I’m aware of for the Nissan Leaf, which has sold in greater numbers while being on the market longer,” he said in an e-mail. “Is there an inherent design flaw in the Tesla’s battery pack that makes it more prone to fires compared to other electric cars? That’s what NHTSA will be determining.”

Gabe Nelson and Automotive News staff contributed to this report.