Two US transportation regulators said Monday they will investigate a fatal car crash involving a Tesla that apparently had no one behind the wheel.

The vehicle was speeding when it hit a tree late Saturday night in Spring, Texas, near Houston. It caught fire, destroying the car entirely and killing two men, police said.

Harris County police official Mark Herman told local media the initial investigation found no one was in the driver's seat of the vehicle. One of the victims was discovered in the passenger chair, and the other in the back seat.

The National Highway Traffic Safety Administration (NHTSA) said it "immediately launched a Special Crash Investigation team to investigate the crash."

"We are actively engaged with local law enforcement and Tesla to learn more about the details of the crash and will take appropriate steps when we have more information," the agency said in a message to AFP.

The National Transportation Safety Board (NTSB) said on Twitter it had dispatched two investigators to the scene, who "will focus on the vehicle's operation and the post-crash fire. NTSB investigators will arrive in the area later this afternoon."

As of Sunday, local investigators had not determined whether the driver's side airbag deployed, or if the vehicle's driver assistance system was deployed at the time of the accident.

Tesla
US regulators have not yet determined whether driver assistance technology was involved in the crash of a Tesla that killed two people in Texas Photo: AFP / David GANNON

The circumstances of the accident have provoked numerous reactions on social media, re-launching the debate on Tesla's existing semi-autonomous capabilities, such as the "Autopilot" software that allows the car to park on its own or navigate on the highway.

People can also buy a more expensive version called "FSD," for "full self-driving," even though the driver is not supposed to let go of the steering wheel.

"Data logs recovered so far show Autopilot was not enabled & this car did not purchase FSD," Tesla boss Elon Musk tweeted Monday.

"Moreover, standard Autopilot would require lane lines to turn on, which this street did not have," he added, responding to a Wall Street Journal article that cited several automobile safety experts, who expressed concern at the potentially risky addition of such autonomy features.

Tesla warns that driver assistance systems Autopilot and Full Self-Driving Capability do not make the vehicles autonomous, and that active supervision is still required.

Musk, however, regularly praises advances made by his company in self-driving technology.

Hours before the crash, he tweeted, "Tesla with Autopilot engaged now approaching 10 times lower chance of accident than average vehicle."

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