Detectives are urging people to vigilant following reports of scams in Wakefield.
They are investigating two offences in the Thornleigh Avenue area of the city in which men claiming to be traders have tried to trick elderly and vulnerable people.
Police said the first incident on June 16 involved two "smartly dressed" men telling a man in his 80s that solar panels installed on his home needed work.
They conned the pensioner into taking them to the bank and giving them cash for the work, which never took place.
A second incident was reported in the same area on June 27, when two to three men managed to trick their way into a house.
Detective Inspector Dave Watts of Wakefield District CID, said: "A number of enquiries are ongoing into these incidents with our colleagues in Wakefield District NPT.
"The individuals that commit this type of offence use a variety of different excuses as why their victims should give them money ranging from pretending that urgent work is required on their home to claiming to have been sent from a company or organisation to check on a utility in or around the home.
"We are urging all residents to be vigilant when answering their door to uninvited tradespeople or salespeople, to always ask for identification and to never leave an uninvited caller alone in their homes, even for a moment.
"If you feel suspicious or unhappy about any caller to your home then you should ask them to leave the premises until you have had an opportunity to clarify whom the caller is. All genuine callers will have good quality identification and have a contact number that you can ring to confirm who they are."
Anyone who may have witnessed the suspects in the Thornleigh Avenue area over the last week or who has been approached by two men in the local area in similar circumstances is asked to contact Wakefield District CID on 101 referencing crime number 13170296668
Information can also be passed anonymously to the independent Crimestoppers charity on 0800 555 111.