A London NHS hospital trust has found four discs, containing 18,000 staff details, that had been thought lost.
The discs, which contained payroll details, went missing earlier this month.
The discs were handed into the finance department of the Whittington Hospital NHS Trust last Friday after a letter was sent out to staff notifying them of the loss, a hospital spokesperson told ZDNet.co.uk.
David Sloman, chief executive of the trust, apologised to staff and said the hospital's data-handling procedures were under review.
"I remain apologetic that we have caused [staff] any anxiety and hope that they feel that we have supported them appropriately throughout the incident," said Sloman. "It is essential that we learn from this. [We] are in the process of further reviewing our procedures to ensure that they are as tight and robust as they can be."
The discs had been protected with alphanumeric passwords, a practice that has been criticised by security experts, who say that such passwords are easy to crack.