Earlier this week, the Social Security numbers of retirees from the California Public Employee's Retirement System (CalPERS) were printed on brochures then mailed to members.
CalPERS released a statement today apologizing for the data breach.
"We sincerely apologize and regret this unfortunate incident, and we are taking every step necessary to prevent this from happening again," read a letter from CalPERS.
According to the statement, the numbers were printed as "a sequence of numbers without hyphens" and were not released electronically.
"It was printed on one piece of mail that was sent to our retirees' home. While it is unlikely that someone would recognize the series of numbers as being a Social Security number except our members, we consider this an unfortunate and serious incident."
CalPERS noted various corrective measures taken including conducting a review of how the organization receives, stores and processes personal information, and implementing mandatory information security awareness training for all employees.
"Members who have any concerns about fraud and identity theft can protect themselves by placing a fraud alert on their credit files," the statement read. CalPERS also recommends that members check the California Office of Privacy Protection Web Site for information on identity theft.
"Once again, we sincerely apologize for this incident. We take the security of personal information of our members very seriously."