NEW YORK (AP) — Federal regulators have opened yet another investigation into Tesla’s self-driving feature after dozens of cases in which the cars ran red lights or drove on the wrong side of the road, sometimes crashing into other vehicles and causing injuries.

The National Highway Traffic Safety Administration said in a filing that it is looking into 58 incidents in which Teslas reportedly violated traffic safety laws while using the company’s so-called Full Self-Driving mode, leading to more than a dozen crashes and fires and nearly two dozen injuries. The new probe adds to several other open investigations into Tesla technology that could upend Elon Musk’s plans to turn millions of his cars already on the road into completely driverless vehicles with a over-the-air update to their software.

“The ultimate question is, ‘Does the software work?'” asked Seth Goldstein, a Morningstar analyst with a “sell” rating on the stock. Added money manager Ross Gerber, “The world has become a giant testing ground for Elon’s concept of full self-driving, and it’s not working,”

The probe comes as Musk, whose fortune as the world’s richest man derives partly from Tesla’s levitating stock, has promised to roll out hundreds of thousands of driverless taxis in cities around the U.S. by the end of next year.

The new investigation covers 2.9 million vehicles, essentially all Teslas equipped with full self-driving technology, or FSD, a misnomer criticized for lulling drivers into handing full control over to their cars. Tesla has argued to regulators and in court cases that it has repeatedly told drivers the system cannot drive the cars by itself and whoever is behind the wheel must be ready to intervene at all times.

In the new probe, regulators reported that many of the Tesla drivers involved accidents said the cars gave them no warning about the unexpected behavior.

Tesla stock fell nearly 3% at one point Thursday but closed with a loss of just 0.7%.

The agency behind the latest probe, NHTSA, opened an investigation last year into driver-assistance features in 2.4 million Teslas after several crashes in fog and other low-visibility conditions, including one in which a pedestrian was killed. NHTSA also opened an investigation earlier this year for a “summon” technology that allows drivers to tell their cars to drive to their location to pick them up after reports of several fender benders in parking lots.

Another investigation was launched by the agency in August looking into why Tesla apparently has not been reporting crashes promptly as required.

The FSD system under investigation is what is called Level 2 driver-assistance software that requires drivers to pay full attention to the road. A new version of FSD was introduced earlier this week. The company is also testing a vastly upgraded version that does not require driver intervention, something that Musk has been promising to roll out for years.