Shell has stopped accepting payments authorised by Chip and PIN at 600 of 1,000 UK petrol stations following the discovery of a systematic fraud that resulted in the theft of an estimated £1m from customer accounts. Eight unnamed people have been arrested in the UK on suspicion of involvement in the scam, the BBC reports.

The mechanism of the alleged fraud, which is being investigated by the Metropolitan Police cheque and plastic crime unit, remains unclear. The Association of Payment Clearing Services, the UK banking organisation leading the introduction of Chip and PIN, said that it was confident the problem applied only to Shell and did not impact of the integrity of the payment method more generally.

Shell said the suspension of Chip and PIN in its UK-owned service stations was a temporary precaution. It has reverted to authorising debit and credit card purchases by signature at these outlets. Around 400 Shell petrol stations run on a franchise, and therefore not directly owned by Shell, are continuing to accept Chip and PIN. Shell hopes to act quickly in order to reintroduce the payment method across all its UK petrol stations