Tesla shares are hit by a fire involving the Model S

Electric car maker Tesla's Model S has suffered its third fire in five weeks.

In the latest incident, which took place on Wednesday in Tennessee in the US, 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, following 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.

Analysts said that while the incidents had been sparked by accidents, investors had been worried over 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.