"Outdoor enthusiasts" are being asked by police if they have seen a missing teacher who is an ultra runner.
Nicholas Harper, 50, was last seen as he left his home in Pickering, North Yorkshire, on Thursday morning.
His black Citroen Picasso was found parked about 13 miles away, near Helmsley.
Insp Dan Spence of North Yorkshire Police said: "We remain very concerned for Nicholas' safety."
He said the student teacher is an ultra runner and could run long distances.
"We are therefore appealing to outdoor enthusiasts who believe they may have seen Nicholas over the weekend to please contact us along with anyone who is out and about in the area today," Insp Spence said.
Specialist police teams are continuing searches north of Helmsley.
Over the weekend, police and volunteer search and rescue teams used dogs, drone cameras and the police helicopter.
Insp Spence also appealed directly to Mr Harper to contact his family.
Mr Harper is white, 5ft 5ins tall with dark brown hair and a full beard and was last seen wearing a three-piece suit and shirt.