The chairman of the U.S. National Transportation Safety Board (NTSB) said Tuesday “operational limitations” in the Tesla Model S played a “major role” in the May 2016 crash that killed a driver using the vehicle’s semi-autonomous “Autopilot” system.

Reuters reported Monday that the NTSB is expected to find that the system was a contributing factor. The system is expected be labeled a contributing factor in the crash because it allowed drivers to avoid steering or watching the road for lengthy periods.

Reuters (Reporting by David Shepardson; Editing by Chizu Nomiyama)