Electric carmaker Tesla's Model S has suffered its third fire in five weeks.
In the latest incident, which took place on Wednesday in the US state of Tennessee, a fire broke out in a car after it hit debris on the road.
Tesla said the fire did not start spontaneously but was the result of the accident. The previous two fires have also been related to accidents.
The firm's shares fell more than 7% on Thursday, after a 14% fall on Wednesday triggered by weak earnings.
The company reported that it made a net loss of $38m in the July-to-September period.
In the latest incident, the front of a Tesla vehicle burst into flames after it ran over a tow bar near the town of Smyrna, Tennessee.
Analysts said that while the fires had been the result of accidents, investors had been worried about any potential impact on the firm.
"For a company with a stock price based as much or more on image than financials, those recurring headlines are highly damaging," said Karl Brauer, a senior analyst with Kelley Blue Book.
Adam Jonas, an analyst with Morgan Stanley, added that the risk of a formal investigation by US safety regulators "could raise near-term concerns to a higher level in terms of cost, image and production disruption".
Tesla's shares fell 7.5% to close at $139.7 on Thursday.
In October, a Model S caught fire after the driver ran over what Tesla said was "an extremely large object" near Seattle, Washington state.
After the fire, officials at the National Highway Traffic Safety Administration had said they found no evidence to indicate that it resulted from defects or violations of US safety standards.
The second incident took place in Mexico later in the month. According to reports a car caught fire after it drove through a roundabout, crashed through a concrete wall and hit a tree.
Tesla said it is investigating the latest incident in Tennessee to find out what had caused the fire.
"Our team is on its way to Tennessee to learn more about what happened in the accident," Tesla spokeswoman Elizabeth Jarvis-Shean said in a statement.
"We will provide more information when we're able to do so."
The firm's chief executive, Elon Musk, has previously said that electric cars are safer than conventional cars.