WASHINGTON (Reuters) – The U.S. National Transportation Safety Board (NTSB) will meet on Feb. 25 to determine the probable cause of the 2018 fatal crash of a Tesla Inc (TSLA.O) vehicle in Mountain View, California, the agency said. The board will hold a hearing on the 2017 Tesla Model X crash that killed the its driver, 38-year-old Apple engineer Walter Huang, who was using the vehicle’s advanced driver assistance system known as Autopilot. The NTSB and National Highway Traffic Safety Administration (NHTSA) are investigating a number of crashes in which Autopilot is believed to have been in use. The crashes raised questions about the driver-assistance system’s ability to detect hazards, especially stationary objects. There are mounting safety concerns about systems that can perform driving tasks for extended stretches of time with little or no human intervention, but which cannot completely replace human drivers. NTSB makes safety recommendations but cannot compel action, while NHTSA can order a recall if it deems a vehicle poses an unreasonable safety risk. Last week, NHTSA said it was launching an investigation into the Dec. 29 crash of a Tesla (TSLA.O) Model 3 that left a passenger dead after the vehicle collided with a parked fire truck in Indiana. That crash is the 14th involving Tesla that NHTSA’s special crash investigation program has taken up in which it suspects Autopilot or another advanced driver assistance system was in use. It is the third Tesla crash NHTSA has said it was investigating in recent weeks. Autopilot had been engaged in at least three Tesla vehicles involved in fatal U.S. crashes since 2016, including the 2018 Mountain View crash. Tesla did not immediately comment. NHTSA is also probing another Dec. 29 fatal crash of a Model S Tesla in Gardena, California. In that incident, the vehicle exited a freeway, ran a red light, and struck a 2006 Honda Civic, killing its two occupants. The NTSB has criticized Autopilot’s lack of safeguards. It said in September that its probe of a 2018 Culver City, California, Tesla crash found the system’s design “permitted the driver to disengage from the driving task.” Tesla and NHTSA both advise drivers to keep their hands on the steering wheel and pay attention at all times while using Autopilot. Tesla says Autopilot “enables your car to steer, accelerate and brake automatically within its lane,” but does not make the vehicle autonomous. Some drivers say they are able to keep their hands off the wheel for extended periods when using the system.