Bank customers are being urged to check their accounts after a sophisticated cloning device was found in Chelmsford.
The device was discovered by a man using the cash machine outside Tescos in Springfield Road on Friday morning.
A false front had been fitted over the machine, and there was a minute camera trained on the keypad.
Police believe the find has foiled a highly professional fraud but warn that some card-users may already have fallen victim to the scam.
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