Up to 27,000 Pittsburgh hospital workers' personal information could be at-risk following a company data breach.

The University of Pittsburgh Medical Center (UPMC) suffered a data breach in February that was initially thought to have affected approximately 300 people, according to the Pittsburgh Post-Gazette. Yesterday, however, a UPMC spokeswoman announced that at least 788 employees were victims of tax fraud as a result of the attack.

The hospital is still coordinating with the Internal Revenue Service (IRS), Secret Service and Federal Bureau of Investigation (FBI) to determine the breach's source. UPMC also contacted all the possibly affected employees, according to the spokeswoman, Gloria Kreps.

A Pittsburgh-based lawyer filed a lawsuit seeking class-action status on behalf of employees whose names were used to create fraudulent bank accounts and tax returns.

[A version of this story has been updated to clarify that UPMC is located in Pittsburgh.]