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.
Firefighters arrived within 3 minutes of the first call. It's not clear from records how long the firefighting lasted, but crews remained on scene for 2 1/2 hours.
Tesla said the flames were contained to the front of the $70,000 vehicle due to its design and construction.
"This was not a spontaneous event," Jarvis-Shean said. "Every indication we have at this point is that the fire was a result of the collision and the damage sustained through that."
There was too much damage from the fire to see what damage debris may have caused, Webb said.
The automobile website Jalopnik.com posted photos of the blaze that it says were taken by a reader, along with a video.
Shares of Palo Alto, Calif.-based Tesla have risen more than 400 percent this year. 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 $12.05 to $180.95 Wednesday.
Also contributing to the stock's decline was a rare analyst downgrade. R.W. Baird analyst Ben Kallo cut his rating on the stock from "Outperform" to "Neutral," telling investors that while he's still bullish on Tesla's long-term prospects, the company has "significant milestones" during the next 18 months that come with risk.
The company's battery system and the Model S itself have received rave reviews, including a top crash-test score from the National Highway Traffic Safety Administration and a tie for the highest auto rating ever recorded by Consumer Reports magazine.
But lithium-ion batteries have raised concerns in other vehicles.
Two years ago, battery fires broke out in three Chevrolet Volt plug-in hybrid cars after crash-testing, but NHTSA investigators determined that the Volt was no more risky than vehicles with conventional gasoline engines.