Police are advising residents to be on their guard and report any incidents of cold callers.
The warning by Ribble Valley Police follows a number of reports of people travelling around the Ribble Valley door-to-door selling. Police said there have been incidents where the sellers have become aggressive towards residents who have refused to buy anything.
Officers want to identify the people who are responsible for the sales and are asking members of the public to contact them if anyone calls at their door in similar circumstances or if they have been targeted already.
A police spokesman said: "Please be cautious when purchasing items from cold callers and if there are any incidents where you feel threatened by sellers please obtain details i.e names and car registrations. To contact police, please call 101."