The personal details of 34,000 customers of investment bank Morgan Stanley could have fallen into the wrong hands after compact discs went missing during transit.
The discs were password protected, but not encrypted.
The data included account and social security numbers, according to reports. The bank said it has not seen any criminal intent or misuse of the missing data.
Morgan Stanley is not the first company to lose computerised customer information in transit.
Zurich Insurance UK lost a computer tape containing information about almost 50,000 customers when it was being transferred to a storage centre in South Africa. It was later fined £2.275m by the Financial Services Authority (FSA) for not having the controls to prevent the loss of confidential personal data.