Dozens of boxes of classified government documents can't be accounted for by the National Archives and Records Administration (NARA) in its records center outside of Washington, D.C. It's the third instance since 1998 that secret records have been discovered to be missing from the agency.

Eighty-one boxes containing top secret information, or restricted data -- such as nuclear weapons information -- from the Office of the Secretary of Defense and several U.S. Navy offices are absent from the Washington National Records Center of NARA, according to a three-year investigation conducted by NARA's Office of the Inspector General between 2007 and December 2010.

According to the report, which was released in response to a Freedom of Information Act request by the Washington Times, this isn't the first time the organization has lost track of confidential government documents. As of March 2011, an additional 2,757 boxes of documents couldn't be located or accounted for, more than 1,500 of which are classified at the secret or confidential level. Each box can reportedly hold up to 2,500 sheets of paper.

While the investigation concluded the missing records weren't removed as a result of theft or espionage, in a 2009 letter to the agency's then-Acting Archivist, NARA Inspector General Paul Brachfeld wrote there was an unacceptable and potentially dangerous status of classified records management and storage at the WNRC in Suitland, Maryland.

NARA officials told the Washington Times this week that bad data is responsible for the discrepancy, emphasizing the missing items only represent a fraction of the millions of boxes stored at the Washington National Records Center.

It isn't the first time the inspector general's office has raised concerns about security practices at the facility. The office reportedly conducted previous inventories of classified materials in 1998 and 2004, concluding on both occasions that boxes of documents were unaccounted for.

According to those staffers that can recall, minimal corrective actions were taken, according to the inspector general's office in the most recent report, noting that security procedures are in urgent need of reevaluation.

For instance, the office produced a list of additional security violations recorded during the period of its investigation that represent elevated security concern, including: classified records being left in an unsecured hallway at WNRC; classified records that were improperly shipped to the wrong federal office and classified documents being openly left on an employee's desk in an unsecured area of WNRC.

The challenges faced at WNRC present no small obstacle. However, if NARA is to truly be a 'national security agency' and provide the federal government with safe, secure and accessible classified storage facilities, then this challenge must be met with an aggressive and overarching approach, states the report. At some point, the originating agency will have to make a determination on the effect of the missing materials... have on national security.

The 81 missing boxes in question originated from the Office of the Secretary of Defense, the U.S. Army Chief of Staff, the Commerce Department's Bureau of Export Administration, the Atomic Energy Commission, the Department of Energy, the National Imagery and Mapping Agency, and four separate offices of the U.S. Navy.

The Federal Bureau of Investigation has been notified of the missing classified material, as directed by the Department of Justice.

About 250,000 boxes of documents enter the WNRC each year. The agency doesn't own the documents; it acts as a custodian, storing them temporarily until they are either destroyed or turned over for permanent placement in the National Archives.