Police have issued a warning after nine people in Essex, including one in Braintree, were tricked out of £19,000 by telephone fraudsters.
Most of the incidents, which all happened last month, were in the west of the county, with three in the Waltham Abbey area, two in Buckhurst Hill, and one each in Epping, Harlow, and Little Hallingbury.
However, the ninth incident happened in Braintree.
Some £11,000 was taken from the victim in Little Hallingbury, while the other amounts ranged from £300 to £2,500.
The victims were all phoned by callers claiming to be police, bank officials or shop staff and were told that their bank cards had been used fraudulently.
They were told their bank cards or cash from their accounts was needed for forensic examination by police.
Taxi firms or couriers were to sent to victims’ homes to collect the cash or cards.
In some cases the victims were also asked to pay up to £40 for the cost of cabs.
Essex Police said the scam had been going on across the county since the start of 2013, with more than 600 thefts and attempted thefts reported since last January.
In total, more than 90 people have now been tricked out of money and more than £309,000 has been stolen.
Six people have been arrested in connection with the investigation.
Despite extensive publicity campaigns, police said elderly and vulnerable people were still falling for the scam.
DS Neil Hudson said: "It is vital that everyone is always on guard against any telephone callers claiming to be from the police or a bank and asking you to send them money.
“If that happens, put the phone down, wait a few minutes until you get a dialling tone and call Essex Police to report it.
"Some of the tricksters call their intended targets several times in an attempt to convince them that they are genuine callers.
"One trick is to ask people to call back or to call their bank to verify claims that their accounts have been infiltrated. But they stay on the line and when the victim thinks they are starting a fresh call the same tricksters claim to be at a police station or a bank.
"It is important that anyone who is called by these fraudsters lets us know so that we can investigate and establish which different stories are being used by the thieves and to see how they are targeting different areas.”