A Hong Kong-owned restaurant - ranked Australia's biggest - has been blacklisted by credit-card companies after a probe uncovered a suspected multimillion-dollar fraud. Visa, Mastercard, American Express and Diners Club have withdrawn their facilities from the 800-seat Kam Fook Seafood and Shark Fin Restaurant in Sydney's Chinatown. Investigators say the scam - in which customers' details were allegedly used to make clone credit cards - was carried out by part-time restaurant staff working for an international crime syndicate. They say the restaurant's owners and managers - former Hong Kongers Eddie Ng, Paul Lai and John Lau - did not know about the racket. The restaurant's other outlet in the suburb of Hurstville has also been blacklisted. Management was warned by credit-card representatives three months ago that there was a problem, but it continued and this week all credit agreements were cancelled. The suspected fraud comes after the separate arrest of credit-card fraud syndicate members from Hong Kong, the mainland and Malaysia in Australia earlier this year, the Sydney Morning Herald reported. Mr Ng claimed his restaurants had not been given enough time to investigate. 'We have been treated arrogantly with an undeserved heavy hand. We have more than 100 staff and didn't have a chance to find who the suspected culprits were. 'We are willing to co-operate with any investigation,' he said.