Rocky Mount, N.C. — North Carolina Highway Patrol troopers followed department policies and procedures last month in responding to an accident on Interstate 95 that killed a South Carolina couple, the patrol said Wednesday.

The bodies of Wayne Anthony Guay, 57, and Dianne Guay, 55, of Myrtle Beach, S.C., were found Dec. 11 inside their white Mazda in a swampy area between I-95 mile markers 139 and 140 in Nash County.

The Guays, who were on their way to visit family members in Queens, N.Y., for an early holiday, had been reported missing on Dec. 7.

A passing motorist called Nash County 911 on Dec. 7  to report that a car had left the highway and had landed in a water-filled ditch. Troopers and other emergency personnel were dispatched to the area but couldn't find anything.

A state Department of Transportation worker later found the car.

Surviving members of the Guay family have said the outcome would have been different if authorities had searched longer. Col. Fletcher Clay, who heads the Highway Patrol, ordered an investigation into the response to the crash.

Lt. Everett Clendenin, of the state Highway Patrol, said officials looked at the information the trooper had and determined he did what any trooper would have done under the circumstances. The trooper even drove the four-mile route a second time, he said.

Clendenin also said there were no marks or debris indicating where the car left the road.

After reviewing troopers' actions and reports in the case, it was determined there were no violations of departmental policies and procedures, authorities said.

The Highway Patrol's accident reconstruction team continues to investigate the case.