Police are investigating reports of cold callers visiting homes and notes being left on vehicles in Richmond and Catterick.
The incidents occurred in Richmond last night.
Sergeant Lauren Wilkinson, from Richmondshire neighbourhood policing team, said the callers were offering to buy cars.
She added: “In some cases, when owners haven’t been present, a note has been left on vehicles with a contact number asking if people are willing to sell.
“We have a number of lines of enquiry to identify these males which are ongoing.
“Please make contact with the police if you have similar callers to your door so that we can try to locate any potential offenders.
“Although the males were in Richmond yesterday, we have had further reports from the Catterick area about similar incidents in recent weeks.”
Police say that over the past month they have recorded a number of suspicious incidents involving empty properties where offenders have gained entry.
Sgt Wilkinson added: “Please ensure that if you have any properties currently empty/awaiting tenants that these are suitably secured.
“CCTV is a great deterrent and assists us with identifying offenders so if you have the option to install this please do.
“We will be upping our patrols around vacant properties and any youths/offenders identified will be dealt with positively.
“As always, should you need to report a crime to us please do so on 101 or 999 if an emergency.”
