The US government is investigating reports of Tesla cars braking unexpectedly on motorways.
The so-called "phantom braking" problem is being looked at by US regulator the National Highway Traffic Safety Administration (NHTSA).
It received 354 complaints in the past nine months and its investigation will cover approximately 416,000 Tesla Model 3 and Model Y vehicles from 2021-22.
Drivers say the issue occurs using the Autopilot driver assistance system.
The feature gives the vehicle control over some elements of braking and steering when driving, although it is not a substitute for a human driver.
Despite the name, Tesla recommends drivers remain vigilant and supervise their vehicle, noting the Autopilot ADAS system "does not make the vehicle autonomous".
In December 2021, it disabled its Passenger Play feature that allowed games to be played on its touchscreen while the car is in motion, leading to an open investigation covering an estimated 580,000 vehicles.
And last August, the NHTSA started to look into the role of the Autopilot system in 11 crashes involving emergency vehicles, covering approximately 765,000 Tesla cars.
The NHTSA's Office of Defects Investigation (ODI) has begun a "preliminary evaluation" into Tesla over the complaints. This is the stage before the agency could officially issue a recall of the vehicles.
It says there have been no crashes, injuries or fatalities as a result of the incidents.