People are being urged to be vigilant following reports of chalk marks being drawn on their property.
A number of concerned residents have contacted police about the suspicious behaviour after seeing marks left near doors and on walls and fences at homes in Raunds and nearby villages.
Two men have been seen in the area, both carrying a laminated card saying they are deaf and that they make their money by selling their artwork.
They both carry a folder with chalk drawings in it.
One of the men is described as being in his late 50s, with curly grey hair and wearing a suit jacket.
The other man is described as being in his 30s, rather scruffy, with dark hair and wearing a hat and a red and navy blue jumper.
A police spokesman said: “We are advising people to remove any markings drawn on their property and to report any suspicious incidents to the police.
“People are also advised never to open the door to unexpected callers or to buy goods from or have work done on their home or garden by people who call at their door.”
Anyone with any information can call Northamptonshire Police on 101 or they can call independent charity Crimestoppers anonymously on 0800 555111.
For home security advice, visit www.northants.police.uk/crimeprevention.
For more information about doorstep crime, visit www.northants.police.uk/lookout.