US safety officials opened a preliminary investigation into Tesla's Autopilot after identifying 11 crashes involving the driver assistance system, officials said on Monday.

The incidents dating back to 2018 included one fatal crash and seven that resulted in injuries to 17 people, according to the National Highway Traffic Safety Administration (NHTSA).

NHTSA "is committed to ensuring the highest standards of safety on the nation's roadways", an agency spokesperson said. "In keeping with the agency's core safety mission and to better understand the causes of certain Tesla crashes, NHTSA is opening a preliminary evaluation into Tesla Autopilot systems."

Tesla founder Elon Musk has defended the Autopilot system and the electric automaker warns that it requires "active driver supervision" behind the wheel, but critics, including in Congress, say the system can be easily fooled and have called for NHTSA to take action.

Tesla did not immediately respond to an AFP request for comment.

The crashes cited by NHTSA involved incidents in which "various Tesla models crashed" in instances where responders were involved, including "some that crashed directly into the vehicles of first responders", the NHTSA spokesperson said. 

Three of the crashes took place in California, with other incidents taking place in Florida, Texas and Massachusetts, among other states. The probe covers models Y, X, S and 3, NHTSA said. 

"A preliminary evaluation starts the agency's fact-finding mission and allows additional information and data to be collected," a NHTSA spokesperson said.

"NHTSA reminds the public that no commercially available motor vehicles today are capable of driving themselves," the spokesperson said.

"Certain advanced driving assistance features can promote safety by helping drivers avoid crashes and mitigate the severity of crashes that occur, but as with all technologies and equipment on motor vehicles, drivers must use them correctly and responsibly."

News of the probe sent Tesla shares sharply lower on Monday. 

Pushing the boundaries 

Musk has a history of skirmishing with regulators, but the controversies have had little effect on Tesla's ascendance over the last year and a half as the company has hit key production targets.

His success in building Tesla from a fledgling startup into an industry pacesetter on electric cars has stood out more as other electric auto startups like Lordstown Motors and Nikola have stumbled. 

At the same time, Musk has sparked blowback from critics as he pushed or flouted the rules on everything from his use of social media to discuss Tesla's operations to his response COVID-19 health protocols required by local officials near Tesla's California plant. 

Advocates with the Centre for Auto Safety, a non-profit group, have pressed US officials to bar the name "Autopilot" since 2019, viewing the moniker as deceptive.

Jason Levine, executive director of the Center for Auto Safety, welcomed news of the NHTSA probe, but said it should go "far beyond" crashes involving first responder vehicles "because the danger is to all drivers, passengers, and pedestrians when Autopilot is engaged", he said in an email.

"Whether Autopilot needs to be disabled, or be required to use driver monitoring systems to prevent these crashes, is a question for NHTSA," Levine added. "But there's no question that something needs to be done quickly to prevent more injuries and deaths."

Testers with the magazine Consumer Reports demonstrated in a video that Autopilot could be fooled into driving with nobody behind the wheel, an exercise also shown in widely-seen videos on TikTok and other social media platforms.

In April, Democratic senators Richard Blumenthal of Connecticut and Ed Markey of Massachusetts urged NHTSA to probe a fatal crash in Texas involving a Tesla after law enforcement said there was no driver behind the wheel.

The senators said Tesla has been criticised for "misrepresenting" its systems and "giving drivers a false sense of security", according to an April 22 letter.

Tesla has said it does not believe the April crash involved Autopilot, and the incident was not included in NHTSA's list of 11 crashes. 

Tesla shares tumbled 5.1 per cent to $680.77 in mid-morning trading.