Following the death of a man who was killed when his self-driving Tesla car crashed in Florida, a US national traffic safety body is opening a preliminary investigation.
A DVD player was found in the vehicle when it crashed, reportedly playing a Harry Potter film.
The US National Highway Traffic Safety Administration said the crash came in a 2015 Model S operating with automated driving systems engaged, and "calls for an examination of the design and performance of any driving aids in use at the time of the crash".
The fatal crash happened on May 7 when a truck made a left turn in front of the 2015 Model S Tesla at an intersection, according to preliminary reports.
The investigation is the first step before the agency could seek to order a recall if it finds the vehicles were unsafe.
Tesla said in a blog post that this is the first known fatality in just over 130 million miles where Autopilot was activated.
The vehicle brand 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".
The company said "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 bottom of the trailer hit the windshield of the Model S, killing the occupant.
Tesla said that "Autopilot is getting better all the time, but it is not perfect and still requires the driver to remain alert. Nonetheless, when used in conjunction with driver oversight, the data is unequivocal that Autopilot reduces driver workload and results in a statistically significant improvement in safety when compared to purely manual driving."
A lawyer for a truck driver said his investigators had spoken to a witness who said the DVD player was playing a Harry Potter video after the accident, but he was unable to verify that beyond the witness account.
"There was a portable DVD player in the vehicle," confirmed Sergeant Kim Montes of the Florida Highway Patrol in a telephone interview.
She said there was no camera found, mounted on the dash or of any kind, in the wreckage.
Paul Weekly of Tampa, the lawyer for the truck driver, said, "As to the video, there was a witness who came to the scene immediately after the accident occurred, and we can't verify it at this point."
The truck driver, Frank Baressi, said the impact of the Model S "lifted the trailer up and jolted the heck out of it when he went under it. It sheared the top of the car right off."
Mr Weekley said that the top third of the Model S was sheared off the sedan while the rest of it went under the trailer and travelled another 213m on the road and 61m off the paved surface before coming to rest.
Mr Weekley said the centre console of the car was not seriously damaged, meaning that the electronic data recorder, the so-called "black box" for the car, should have been intact.
The recorder had been removed from the Model S before his investigators were able to see it, he said.