A elderly woman lost what was described as a “considerable amount of money” after two men pretending to be from a water company had her listening to a running tap while they searched her home.
The distraction burglary took place in the village of Northborough on May 24.
Community safety officer Carol Aston said: “This type of crime has not been seen in Peterborough for some years now - there have been two more in Huntingdonshire villages on 17th and 24th May.
“Nationally there has been an increase and water companies are urging families and neighbours of elderly people they are aware of to set up a password scheme and try and encourage the elderly person to use it.
“Please pass this message to as many people as you can to try and get the message across to ask for ID and ask for a password if anyone says they are there to do work. If you see anything suspicious please report it to the police by phoning 101.”
The police message comes less than after Anglian Water warned Peterborough residents of bogus callers claiming to be from the water company operating in the city.
The firm said it had received reports of fraudulent people posing as its employees and was urging residents to check the identification of any callers.