The Social Security Administration (SSA) says it has carried out the largest cleanup of Social Security Numbers (SSNs) in its 91-year history, correcting about 50 million records, according to the agency. SSA said the work covers nearly 15 percent of all active SSNs across approximately 330 million U.S. citizens, and the figure was also confirmed to Fox News.

As part of the effort, SSA said it added 17 million dates of death to records that previously lacked them, using internal SSA systems and Department of State data. Using data from the Department of Homeland Security’s Systematic Alien Verification for Entitlements (SAVE) service, SSA updated approximately 25 million records that were missing citizenship information.

SSA said it is currently correcting an additional 8.5 million records with inaccurate citizenship status. It also said it has put stronger internal controls in place to prevent errors caused by manual data entry.

“The Social Security Number database is our country’s books and records,” SSA Commissioner Frank J. Bisignano said. “Accurate SSN records prevent fraud across federal programs and support the proper administration of benefits.”

SSA said the corrections have been made since the beginning of the Trump Administration, and that this is the first time the agency has undertaken a record-integrity initiative of this scale.