A DVD player was found in the Tesla car that was on autopilot when its driver was killed in a collision with a truck in May, Florida Highway Patrol (FHP) officials confirm, amid differing reports about whether Harry Potter was playing on the portable system after the accident.

Key points: "There was a portable DVD player in the vehicle," FHP Sergeant says

"There was a portable DVD player in the vehicle," FHP Sergeant says Unverified witness account suggests DVD player was playing Harry Potter after accident, lawyer for truck driver says

Unverified witness account suggests DVD player was playing Harry Potter after accident, lawyer for truck driver says May be weeks before officials make final determination of cause of crash

FHP Sergeant Kim Montes said "there was a portable DVD player in the vehicle," but would not elaborate further. She also said there was no camera found, mounted on the dash or of any kind, in the wreckage.

Whether the player was operating at the time of the crash has not been determined with witnesses who came upon the wreckage of the 2015 Model S sedan giving differing accounts about whether the player was showing a movie.

A man who lives on the property where the car came to rest said when he approached the wreckage, 15 minutes after the crash, he could hear the DVD player.

An FHP trooper on the scene told the property owner, Robert VanKavelaar, that a Harry Potter movie was showing on the DVD player, Mr VanKavelaar said.

However another witness, Terence Mulligan, said he arrived at the scene before the first Florida state trooper and found "there was no movie playing."

"There was no music. I was at the car. Right at the car," Mr Mulligan said.

Questions of why the car did not stop for a turning truck, and whether the victim, Joshua Brown, was watching the road are critical for Tesla Motors Inc.

The electric car maker is facing a preliminary inquiry by federal regulators over the safety of the Model S Autopilot system that was engaged at the time of the crash.

The autopilot system allows the car to keep itself in a lane, maintain speed and operate for a limited time without a driver doing the steering.

Tesla said in a statement: "Autopilot is by far the most advanced driver assistance system on the road, but it does not turn a Tesla into an autonomous vehicle and does not allow the driver to abdicate responsibility."

It could be weeks before officials make a final determination of the cause of the crash, the first known fatality of a Model S driver while using autopilot.

The FHP's Sergeant Montes said a Tesla engineer downloaded the information from the "black box" and shared it with FHP investigators.

A Tesla Model S electric car. ( Supplied: Tesla )

The FHP has the ability to download information from newer vehicles about how the vehicle was being driven before a crash.

But it does not have the ability to download information from Tesla's data system, Sergeant Montes said.

Officials from the National Highway Traffic Safety Administration were alerted by Tesla about the crash, and NHTSA officials first contacted the FHP last week, Sergeant Montes said.

The lawyer for the truck driver, Frank Baressi, 62, said the Model S's data recorder had been removed before his investigators were able to see it.

The victim was identified in police reports and in obituaries as 40-year-old Joshua Brown. He was a Tesla enthusiast and a former Navy SEAL who ran a technology company in Ohio, according to social media accounts and his company's website.

Joshua Brown, who was killed when his car was involved on a crash while in "autopilot" mode. ( Supplied: Nexu Innovations )

A YouTube video account belonging to a Joshua Brown had a recently posted video showing a Tesla Model S automatically able to avoid a truck that veered into its lane.

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 about another 210 metres on the road and 60 more metres off the paved surface before coming to rest.

Mr Baressi, an independent owner-operator, was hauling a half-load of blueberries when the 18-wheeler he was driving made a left turn, attempting to cross the eastbound lanes of US Highway 27 Alternate near Williston, Florida.

Mr Baressi said he had waited to allow another car to go by, then was making the turn when he first saw the Tesla.

"I saw him just cresting the hill so I gave it the gas," said Mr Baressi, who said the Tesla was in the left of two eastbound lanes, or the passing lane.

But by the time the Tesla struck the white trailer carrying the blueberries, "he was in the slow (right) lane ... I thought he had a heart attack or something. I don't know why he went over to the slow lane when he had to have seen me," he said.

Tesla said the white trailer was not easy for the car's cameras to distinguish from the bright Florida afternoon sky.

The crash occurred on a sunny Saturday afternoon in May, according to the initial traffic report of the crash.

Reuters