PITTSBURGH — The personal information of 27,000 University of Pittsburgh Medical Center employees might have been put at risk by identity thieves who apparently used the information of 788 workers to file bogus federal tax returns, the hospital network said.

UPMC notes that no patient information has been lost. When UPMC first confirmed the identity thefts in February, officials believed just 22 workers’ information was used to file bogus returns. UPMC has 62,000 employees.

The IRS says 1.2 million taxpayers were tax fraud victims in the 2012 fiscal year.