The motorist at the wheel of a self-driving car has died after it crashed with a tractor's trailer.

The death is the first reported self-driving fatality reported in the United States.

The male driver of the Tesla 2015 Model S sports car was using the vehicle's "autopilot" automated driving system when the crash with the tractor's trailer happened.

In a statement Tesla said: "neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied," when the tractor made a turn across a road in Florida which the car was travelling on.

The car passed under the trailer, with its underneath hitting the vehicle's windscreen.

Tesla added that the driver of the car must keep their hands on the steering wheel at all times and that they must "be prepared to take over at any time".

The US National Highway Traffic Safety Administration (NHTSA) is opening a preliminary investigation into 25,000 of the vehicles following the crash which happened in May. The investigation is the first step to recalling the cars. The cars can only be recalled if the investigation finds that they are unsafe.

In a blog post Tesla said the death was the first in just over 130 million miles where Autopilot was in use, compared to a death every 94 million miles on average in the US.