A preliminary investigation has been launched after the death of a man in Florida who was driving a Tesla Model S car on autopilot mode.
The crash with a tractor occurred on 7 May and is the first known fatality in more than 130m miles where Tesla's autopilot setting has been activated, the electric car maker said in a statement.
The driver has been named in media reports as 40-year-old Joshua Brown.
The US National Highway Traffic Safety Administration's (NHTSA) inquiry will look into 25,000 Model S sedans that are equipped with the autopilot system.
Tesla said of the crash:
What we know is that the vehicle was on a divided highway with autopilot engaged when a tractor trailer drove across the highway perpendicular to the Model S.
Neither autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied.
The high ride height of the trailer combined with its positioning across the road and the extremely rare circumstances of the impact caused the Model S to pass under the trailer, with the bottom of the trailer impacting the windshield of the Model S.
Had the Model S impacted the front or rear of the trailer, even at high speed, its advanced crash safety system would likely have prevented serious injury as it has in numerous other similar incidents.
Tesla added that the company disables autopilot by default and requires "explicit acknowledgement that the system is new technology and still in a public beta phase before it can be enabled".
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When a driver activates autopilot, they are still instructed to keep their hands on the steering wheel at all times.
The company described the feature as "not perfect" and said its use "still requires the driver to remain alert".
The pioneering electric car manufacturer, headed by Elon Musk, revealed its latest vehicle, the Model 3, in April.