Documents containing names and mortgage details of Leeds Building Society customers have been found on a Belfast city centre street.
The documents were found by a group of young people waiting for a taxi.
The company said it was not possible to identify specific individuals from the papers, but an investigation has begun.
Former assistant information commissioner for Northern Ireland, Marie Anderson, said the company must carry out a review of its security.
Michael Bedwell, who was among the group of young people who found the papers, said they were just swirling around the streets.
"We noticed a lot of them had details, people's names, different numbers," he said.
"I didn't know what they meant or couldn't understand them but they seemed to be related to their bank accounts.
"There was internal e-mails from Leeds Building Society about people's accounts. I wouldn't like my personal details being blown around the streets at two o'clock in the morning in Belfast."
Ms Anderson said she would be concerned if it was her information in the public domain.
"I know Leeds have probably got very tight systems in place but all it takes is one individual to take this sort of information home in a brief case or to leave a file somewhere inadvertently, and we're back to the old human error story."
Breach inquiry
In a statement, Leeds Building Society said: "We have a strict information security framework covering the storage and destruction of all confidential data and all members of staff have been trained and tested on this in 2008.
"From the information supplied to us by the BBC (and from our own investigation) we have established that it is not possible to identify specific individuals from the papers that were found and, therefore, the security of our customer records has not been compromised.
"The information is not sufficient in itself to allow an unauthorised person to access any of the small number of accounts involved.
"However, the fact that the papers were not dealt with through our destruction of confidential waste process is being taken very seriously and an investigation has already started to identify how the breach, which is limited to our Belfast office, has occurred."
^ Back to top | BBC Sport Home | BBC Homepage | Contact us | Help | ©
~RS~q~RS~~RS~z~RS~29~RS~)