Some of the leaked personal client information from South Korea's major credit card firms, possibly amounting millions of cases, appears to have been transferred to personal data dealers, sources said Friday, contradicting assurances by regulators that the leak had been contained. The largest-ever data theft came to light in January when an employee from a personal credit ratings agency, the Korea Credit Bureau (KCB), was found to have stolen the sensitive personal information, including resident registration numbers, bank account numbers and credit ratings, of millions of customers of KB Kookmin Card Co., NH Nonghyup Card Co. and Lotte Card Co.