A citation was issued to the driver of a car that crossed into oncoming traffic on U.S. Highway 550 on Wednesday, resulting in a collision that killed three people.

Kenneth Johnson, 60, of Delta, was issued a citation for careless driving causing death, Colorado State Patrol officials said Friday.

Sgt. Chad Martin said Johnson strayed into oncoming traffic. Johnson, driving a Toyota Avalon sedan, collided with a northbound Nissan Xterra SUV.

Authorities are investigating what caused the Avalon to cross lanes.

Troopers don't suspect alcohol or drugs played a role.

Killed were Ruth Shields, 91, of Durango; John Lyle Bennett, 61, of Olathe; and Keith Duane Marksberry, 61, of Delta.

Shields was a passenger in the Xterra, while Bennett and Marksberry were passengers in the Avalon. Three others were treated for various injuries.

The wreck occurred south of the entrance to Glacier Club, about 14 miles north of Durango.

Shields was an early member of the San Juan Basin Archaeological Society, according to an email from the group. A son, Paul Shields, and daughter Diane Cassidy live in Durango.