Montana Highway Patrol troopers are still putting together the pieces of what caused a fatal car accident that killed two Columbia Falls teens on Friday. Troopers said they spent Saturday interviewing witnesses and family members.

Mercy Peterson, 18, was driving southbound on Highway 2 near Glacier Airport when his car drifted over the center lane and collided head-on with a mini van heading north. Peterson was pronounced dead on scene. His passenger, 17 year old Kayli Wagoner, was transported to Kalispell Regional Medical Center where she died from injuries sustained in the crash.

Troopers tell NBC Montana they still don't know what caused the crash. Blood work taken from Peterson has been sent to the State Crime Lab to be analyzed.