Police have scaled up the search for 75-year-old Hambleton man Colin Leggat.
Mr Leggat was last seen at his home address in the village of Thornton Le Street on Thursday (3 March).
His car remains at his home address and officers believe that he has left home on foot.
The focus of the search is fields and open areas in the vicinity of the village of Thornton Le Street.
Police have used a drone to allow them to view aerial footage of large open areas. The National Police Air Service helicopter, search dogs, volunteer mountain rescue teams and a police underwater search unit have also been deployed.
Mr Leggat was last seen wearing a white checked shirt, green country-style trousers and a thin brown jumper.
Acting Critical Incident Inspector Tom Collins from North Yorkshire Police said: “We are extremely concerned for Colin’s welfare. I urge anyone who is in the Thornton Le Street area to be vigilant and to report any immediate sightings of anyone matching Colin’s description to 999.”
If you have any other information that could aid the search then call police on 101 and quote reference number 12220037935.