An HSBC branch in Hong Kong has lost a server containing the personal details of 159,000 customers.
The server is said to have disappeared early last month during renovation work at the branch.
The missing machine stored customer names, their account numbers and transaction details.
HSBC stressed that the server, which is said to have been protected with "multiple layers of security", did not contain customer Pins or online banking log-in details.
The Hong Kong police and financial authorities are investigating the incident.
In the UK, HSBC recently lost a computer disc containing the personal details of around 370,000 life assurance customers.