It’s emerged a driver of a Tesla has died in a crash while it was in autopilot mode on a road in California.

Tesla says that in the moments before the collision, which occurred at 9:27 a.m. on Friday, 23 March, Autopilot was engaged with the adaptive cruise control follow-distance set to minimum.

“The driver had received several visual and one audible hands-on warning earlier in the drive and the driver’s hands were not detected on the wheel for six seconds prior to the collision,” it says in a blog post. “The driver had about five seconds and 150 meters of unobstructed view of the concrete divider but the vehicle logs show that no action was taken.

“The reason this crash was so severe is because the crash attenuator, a highway safety barrier which is designed to reduce the impact into a concrete lane divider, had been crushed in a prior accident without being replaced. We have never seen this level of damage to a Model X in any other crash.”

America’s National Transportation Safety Board is investigating.