The incident happened around 11.40 am on Friday when a man arrived at the woman’s home claiming to be from the water board.
He persuaded her to let him into the house, saying he needed to test her water pressure and it was an urgent matter.
When he had left, the householder discovered that the upstairs rooms had been ransacked and various items of jewellery and cash stolen. He also took money from her purse.
It is thought he may have let another man into the house while distracting the victim.
Police are now asking anyone with information that can help to trace this individual or individuals.
PC Claire Harman said: “This was a callous and despicable crime against a vulnerable member of our community and we will do everything in our power to bring these individuals to justice.
“In the meantime we would urge everyone to be vigilant and not to allow anyone into their home if they are in any doubt about who they are.
“Don’t allow anyone into your home until you have verified their identity by telephoning their workplace. All legitimate callers will be happy to wait outside until you do this.”
Anyone with information that can assist police to trace these suspects is asked to call 101.