LOS ANGELES (AP) — Authorities say a Tesla involved in a fatal crash on a Southern California freeway last week was operating on Autopilot.

The May 5 crash in the city of Fontana 50 miles east of Los Angeles is under investigation by the National Highway Traffic Safety Administration. The probe is the 29th case involving a Tesla that the agency has responded to.

The California Highway Patrol announced on Thursday that the car was operating Tesla’s partially automated driving system called Autopilot, which has been involved in multiple crashes.

The Fontana crash marks at least the fourth U.S. death involving Autopilot. Tesla did not return a message seeking comment.