A state health department mailed out letters to some 50,000 California residents during the month, erroneously listing their Social Security numbers, alongside the names and addresses, that were written on the envelopes.

The security breach happened in a February 01 mailing which was undertaken by the California Department of Health Care Services. A total of 49,352 letters were sent out as a part of the state's Adult Day Health Care program, and the breach occurred when workers department, while preparing and formatting the mailing lists, mistakenly ended up including the Social Security numbers on the mailing labels. The details have all been confirmed by the officials of the department.

On Monday, the error was officially disclosed, and officials have apologized to all the affected parties, and the agency is now advising beneficiaries on how to protect themselves from probable identity theft.

"The privacy of Medi-Cal beneficiaries is a top priority for DHCS. We have implemented additional safeguards governing the release of Social Security numbers. ... We will redouble our efforts to ensure that all beneficiary information entrusted to the state is aggressively and appropriately protected", said Director David Maxwell-Jolly.