A fatal crash involving an autonomous Tesla car last year was largely the result of human error, investigators have concluded.
The crash happened on May 7, 2016, when a truck turned in front of the 2015 Model S Tesla at an intersection.
A DVD player in the car was reportedly playing a Harry Potter movie at the time of the accident.
Tesla said it was the first recorded fatality in about 200 million kilometres clocked up by Tesla cars using its Autopilot mode.
The US National Transportation Safety Board (NTSB) this weekend said the accident was caused by a "combination of factors".
Firstly, the car allowed the driver - 40-year-old Joshua Brown - to activate its Autopilot mode on a highway, driving at speeds Autopilot was not yet approved for.
The car did however warn Mr Brown several times he should take over the wheel, which he ignored.
Tesla says its Autopilot function isn't a true 'self-driving' mode - it controls steering and acceleration, but still requires the driver to watch what's going on.
Since the accident, Tesla has improved its cars' radar systems to detect obstacles, and cars on Autopilot now start slowing down if the driver ignores the warnings.
The NTSB said it still backs self-driving cars, because 94 percent of accidents are caused by human error - mistakes computers don't make.