A vehicle making an ill-advised pass on U.S. Highway 666 near the New Mexico border smashed head-on into a northbound truck Saturday evening, leaving four people dead and two in critical condition.

Towaoc Police Chief Dusty Whiting said that the accident occurred around 6 p.m. 2 miles north of the state line when Dolly A. Charlie-Duncan, who was driving a 1992 Saturn southbound on Highway 666, attempted to pass a semi tractor-trailer and another passenger vehicle.

"She failed to complete the pass and struck a red 1998 GMC truck that was heading northbound," said Whiting.

Charlie-Duncan and her husband, Benjamin Duncan Sr., both of Shiprock, N.M., were pronounced dead at the scene, Whiting said.

The accident occurred near the old Mancos River Trading Post, according to the report.

Whiting said that two persons in the northbound truck, Marie Thompson and Emma Sandobal, were also pronounced dead at the scene. The other two persons in the truck — Theresa Thompson, who was believed to have been the driver, and Virginia Nez, 43 — were taken by helicopter to nearby hospitals. All were from the Chinle, Ariz., area, Whiting said.

He said that he was unsure which — if any — of the victims were wearing a seatbelt. "Some of the individuals were trapped in the vehicles and others were expelled," he said.

He said that Theresa Thompson and Nez were airlifted to San Juan Regional and Southwest Memorial hospitals initially and then later on to the University of New Mexico Hospital in Albuquerque.

A spokesperson for the UNM Hospital said that on Monday Nez and Theresa Thompson had been admitted to the trauma surgery section of the hospital, where they were still listed in critical condition Monday afternoon. The spokesperson told Towaoc police that Thompson had regained consciousness but that Nez remained unconscious and on a respirator to aid with breathing.

The police chief said the incident is being investigated by the Bureau of Indian Affairs and the Colorado State Patrol.

Alcohol and drugs did not appear to be a factor in the accident.

"It was an improper pass that was the cause of the accident," Whiting said. "We have no reason to suspect that drugs or alcohol were involved."

Whiting said that particular stretch of road, down to the New Mexico state line, is a dangerous area and motorists need to watch out for other traffic.