Thousands of motorists who use a bank card to buy petrol are thought to have lost millions of pounds in an international criminal operation.
Police are investigating complaints from motorists across the UK
It is believed cards are being skimmed at petrol stations, where the card details and pin numbers are retrieved and money withdrawn from the account.
About 200 of the UK's 9,500 petrol stations are thought to have been hit.
The Sri Lankan government claims the rebel Tamil Tigers are to blame but police say there is no definite link.
Police are investigating complaints made in Edinburgh, Norwich, Bury St Edmunds, Peterborough, Nottingham, Leeds, Bristol and Hull.
In Hull, the economic crime section of Humberside Police are checking thousands of receipts for fuel bought with credit or debit cards at one petrol station.
Detective Inspector Paul Welton, of Humberside Police, said "Quite clearly this was well-organised and it was done on an international basis."
Those alleged to have been involved were able to obtain card details and pin numbers and put them together to clone the cards, police said.
The site in Hull is now under new management, and the new owners are not linked to the police inquiry.
Sean Gillespie, one of thousands of possible victims, noticed his bank account was being emptied of small amounts over weeks, amounting to thousands of pounds.
"I knew how much had been taken but how it was taken was an absolute mystery to me," he said.
Other fraud victims have contacted the BBC News website and some said it happened at BP petrol stations.
A BP spokeswoman said between 10 and 12 of their 1,300 sites nationwide had been affected and the firm had issued additional security advice to staff.
She advised customers to insert their bank cards into the chip and pin devices themselves and be careful no-one could see them entering their pin numbers.
Ray Holloway, from the Petrol Retailers Association, said his members had tried to tackle the problem by training staff and checking machinery.
But he added: "The criminal gangs that are involved in this offer quite large sums of money to some employees in order to actually be involved in it."
Most of the UK's petrol stations are independently run which means they are susceptible to being infiltrated by organised crime.
Maxwell Keegel, first secretary of the Sri Lankan High Commission in London, said the Sri Lankan government had evidence to suggest the scam was being used to fund the Liberation Tigers of Tamil Eelam (LTTE).
Independent security sources told BBC correspondent Keith Doyle these claims were credible.
But a Humberside police spokesman said: "Our evidence does not suggest there is a definite link with Sri Lankan gangs."
And a statement by the LTTE said the allegations were no more than an example of the "spin doctoring of the Sri Lankan government".
The statement continued: "Neither the majority of the Tamil diaspora nor the LTTE involve itself in activities in other countries that are against laws of that country."