On Wednesday November 8 an 82-year-old female in Grantham handed over Â£7,000 and on Saturday November 11 a female of the same age living in Long Bennington gave fraudsters Â£4,000.
It follows an incident on Thursday October 26 when an 81-year-old man was conned into handing over Â£10,000 to fraudsters.
In the space of three weeks more than Â£20,000 has now been extorted by criminals claiming that they work in police departments investigating fraud.
Detective inspector Jon Shield from Grantham CID said: “This scam is much more sophisticated than you might think. What is catching people out is that the fraudster will ask the victim to hang up the phone and call 999 or 101 to check that the call is genuine.
“The victims comply with this but the fraudster doesn’t terminate the call, which keeps the line open, and the fraudster poses as a police official once more and confirms that the victim needs to withdraw cash. This is catching people out across the country as many don’t realise that only the caller can terminate a call – otherwise the line remains open.
“This scam is purposefully targeting the elderly so please be extra cautious and don’t take it for granted if someone claims to be a police officer. We would never ask anyone to withdraw money from their bank accounts.
“If you receive a call of this nature or have any suspicions at all please hang up the phone. If the problem persists please report it to us by calling 101, make your bank aware and inform your family or friends.
In the original case, the victim was contacted by someone claiming to be a Sergeant working for a fraud office. He was told that his local bank branch was being investigated and asked him to withdraw Â£10,000 to help their investigation. The victim was strictly told not to mention the investigation to the bank when he went to withdraw the money. After making the withdrawal, the man returned home and a courier visited, taking the money from him. The victim had been told that this would happen so cooperated.
In both of these new cases a courier has again visited the victims home addresses to take away the cash. Investigations are ongoing.
Anyone with information should call police on 101.