Shortly before 3pm yesterday, a man knocked on a door in Gressingham Drive, Lancaster, and told the lady there he was from the water board and needed to check her kitchen taps.

She let him in, but as she came out of the kitchen, she saw two other men running out of the house. It is as yet unclear whether anything was stolen.

Then, at around 3.40pm, police were informed of three men claiming to be from the council trying to gain access to a house in Ashton Road because of water problems in the area.

But the male occupier challenged the men and asked for identification and the trio left.

An 84-year-old woman in Park Square was visited by a male and female, claiming to be from the water board, at around 4pm.

The woman was taken into her kitchen while one of the offenders searched the property before making off with £1,000.

The offenders were described as a female with short black hair, going grey, in her forties and of slim build, wearing black clothing and gloves and a white male in his thirties, of medium build, with combed back hair and wearing black clothing.

Then, at around 5pm, an 86-year-old woman was targeted in Scafell Road.

A man visited the property saying he was dealing with a water problem and then made the pensioner empty out her kitchen cupboards before asking her to run her upstairs taps.

Meanwhile, he stole £150 before making off.

Det Insp Glen Oldham, Lancaster CID, said the four incidents could be linked and is urging residents to check the identification of cold callers and call their employers to verify who they are.

"These are heartless crimes which have targeted vulnerable elderly people in their own homes," he said.

It is thought the offenders may have been using a blue Ford Focus ST 3, registration PE06 EXX.

Anyone who has seen the vehicle, or has any information, should contact Lancaster CID on 01524 63333 or Crimestoppers in confidence on 0800 555 111.