Since Tuesday 12 April 2011, the local Safer Neighbourhood Team has received several reports of incidents in and around the town.
On Tuesday 12 April officers received reports that the Parochial Hall in Sowerby had been defaced, with offenders spraying paint onto an exterior wall.
Later the same day, a car in South Terrace, Sowerby, was damaged after a line of paint was sprayed down its side.
The following day a member of the public reported that blue paint had been sprayed onto the wall of a footpath which runs alongside Cod Beck and paint was also found under the road bridge which runs over the beck.
At around 8.20pm on Thursday 14 April 2011, three men were seen to spray paint onto a wall on Chapel Street, before making off in the direction of Town End.
Police are appealing for any who witnessed the incidents or knows who is responsible for the graffiti to come forward.
Sergeant Lindsey Midgley, of Thirsk Safer Neighbourhood Team, said: “These incidents are obviously upsetting for the people of Thirsk who take great pride in their community.
“I am appealing to anyone who can help the police investigation to get in contact and help find those responsible.”
Anyone with information that can help the police with their enquiries is urged to contact Sgt Lindsey Midgley, of Thirsk Safer Neighbourhood Team, on 0845 60 60 24 7, quoting reference number 12110058947.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.