Investment bank UBS is investigating the disappearance of a hard disk from its Tokyo office which contains confidential customer data.
The hard disk contains data on 15,500 accounts, which in some cases include client names, addresses, telephone numbers, account numbers, transaction records and account balances.
UBS says the loss of the disk, which contains data on past and present clients, came to light during a global upgrade of its data archiving system.
An investigation has been launched. The bank says at this stage, it has no reason to believe the data have been used improperly but it is working with the regulators to take appropriate remedial action.
In December last year Bank of America "lost" computer tapes containing charge card account information for 1.2 million government card holders during transfer to a backup data centre.