The Oregon State Police is looking for witnesses who may have left the scene of a double-fatal traffic crash July 19 north of Madras without talking to police.

The crash, at about 5:30 p.m. on U.S. Highway 97 seven miles north of Madras, killed Warren Chester Ward, 91, of Chula Vista, Calif., and Harold M. Curtis, 71, of Antelope. Ward, driving a 2013 Subaru Legacy and attempting to pass a truck, collided head-on with a 1991 Ford Explorer driven by Curtis, according to OSP.

Troopers interviewed only one witness who stayed at the scene; they’re interested in contacting the driver of a white tractor-trailer parked on the southbound road shoulder as troopers arrived that day.

The truck pulled away before troopers could determine whether the driver was a witness to the crash, according to OSP. The license plate appeared to be from a state other than Oregon.

Any witnesses not previously contacted and interviewed about the crash are urged to call Trooper Justin Lane at 541-388-6213, ext. 5128.