WASHINGTON — U.S. auto safety regulators said Thursday they are opening a special crash investigation into a fatal accident in Virginia involving a Tesla Model Y suspected of relying on advanced driver assistance systems and striking a heavy truck.

The National Highway Traffic Safety Administration is probing a July 19 fatal crash in which the driver of a Tesla died after striking a tractor-trailer truck in Warrenton, Va.

The Fauquier County Sheriff’s Office said the 57-year-old Tesla driver was killed after the tractor trailer was attempting to turn onto a highway from a truck stop. The Tesla struck the side and went underneath the tractor trailer and the driver was pronounced deceased on the scene. The driver of the tractor trailer was issued a summons for reckless driving.

Since 2016, the U.S. auto safety regulator has opened more than three dozen Tesla special crash investigations in cases where driver systems such as Autopilot were suspected of being used, with 23 crash deaths reported to date.

Autopilot is a feature intended to steer, accelerate and brake cars automatically within their lane, while enhanced Autopilot can assist in changing lanes on highways. Tesla, which did not respond to requests for comment, says the system requires active human supervision.

NHTSA last month opened another special crash probe into a July 5 fatal accident in California involving a 2018 Tesla Model 3. The South Lake Tahoe crash killed the 17-year-old driver of a 2013 Subaru Impreza after a head-on collision with the Tesla Model 3 and fatally injured a three-month-old passenger in the Tesla who died several days later.

NHTSA typically opens more than 100 “special” crash investigations annually into emerging technologies and other potential auto safety issues that have, for instance, previously helped to develop safety rules on airbags.

Those are separate from defect investigations opened by the agency to determine if a safety recall is warranted.

In June 2022, NHTSA upgraded to an engineering analysis its defect probe into 830,000 Tesla vehicles with driver assistance system Autopilot and crashes with parked emergency vehicles, including fire trucks. The probe was first opened in August 2020.

Transportation Secretary Pete Buttigieg last month declined to offer an update on the status of the Tesla Autopilot investigation but told Reuters “we’re moving as quickly as we responsibly can.”