The driver of a Tesla S sports car using the vehicle's "autopilot" automated driving system has been killed in a collision with a truck - the first US self-driving car fatality.
The National Highway Traffic Safety Administration (NHTSA) says preliminary reports indicate the crash occurred when a lorry made a left turn in front of the Tesla at a junction.
NHTSA says the Tesla driver died due to injuries sustained in the crash, which took place on May 7 in Williston, Florida.
The US government is investigating the design and performance of Tesla's system.
Tesla said on its website neither the driver nor the autopilot sensors noticed the white side of the lorry, which was perpendicular to the Model S, against the brightly lit sky, and neither applied the brakes.
"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," the company said.
The windscreen of the Model S collided with the bottom of the lorry.
The company said the accident led to the first known death in over 130 million miles of autopilot operation.
It said the NHTSA investigation is a preliminary inquiry to determine whether the system worked as expected.