HAMPTON, Ore. -

A 55-year old Bend man has improved to serious condition at a Bend hospital, four days after his motorcycle ran off a remote section of Highway 20 and crashed near Hampton in eastern Deschutes County, authorities said.

Oregon State Police said Saturday they were continuing their investigation into the cause of the crash, which occurred around 3 p.m. Friday near milepost 68.

A 2005 Honda motorcycle operated by Brent D. Morgan was eastbound on Highway 20 near milepost 68 when, for an unknown reason, it traveled off the highway. Morgan was thrown from the motorcycle and critically injured, troopers said.

Three nurses traveling through the area came upon the crash scene and provided initial medical treatment. Troopers said an air ambulance responded and flew Morgan to St. Charles-Bend, where he has improved to serious condition, a nursing supervisor said Tuesdsay night.

The highway was closed for about 35 minutes for the helicopter to land and pick up the patient.

Troopers said Morgan was wearing a helmet, and that there was no evidence any other vehicles were involved in the crash.

OSP Burns office Trooper James King is the lead investigator.

Meanwhile, Bend pastor Dan Dillard, 61, remained in serious condition at the Bend hospital Tuesday, more than three weeks after his motorcycle and a car collided at a northeast Bend intersection.