Police are warning residents living in the Boultham Park, Birchwood and Moorland areas of Lincoln to be vigilant following several reports of suspicious behaviour.
Lincolnshire Police have received two reports from residents who have been targeted by someone claiming to be a window cleaner.
In both cases a small amount of cash was handed over despite their windows not being fully cleaned.
Another report was in Westbrooke Road where a man was handing out flyers for conservatories without ID.
A spokesperson for Lincolnshire Police said: “Please look out for your neighbours, especially if they are elderly or vulnerable, and report anything suspicious on 101.”