State Department officials removed files from the secretary's office related to the Benghazi attack in Libya and transferred them to another department after receiving a congressional subpoena last spring, delaying the release of the records to Congress for over a year.

Attorneys for the State Department said the electronic folders, which contain hundreds of documents related to the Benghazi attack and Libya, were belatedly rediscovered at the end of last year.

They said the files had been overlooked by State Department officials because the executive secretary's office transferred them to another department and flagged them for archiving last April, shortly after receiving a subpoena from the House Select Committee on Benghazi.

The new source of documents includes electronic folders used by senior officials under Secretary of State Hillary Clinton. They were originally kept in the executive secretary's office, which handles communication and coordination between the secretary of state's office and other department bureaus.

The House Benghazi Committee requested documents from the secretary's office in a subpoena filed in March 2015. Congressional investigators met with the head of the executive secretary's office staff to discuss its records maintenance system and the scope of the subpoena last April. That same month, State Department officials sent the electronic folders to another bureau for archiving, and they were not searched in response to the request.

The blunder could raise new questions about the State Department's records process, which has come under scrutiny from members of Congress and government watchdogs. Sen. Chuck Grassley (R., Iowa), chairman of the Senate Judiciary Committee, blasted the State Department's Freedom of Information Act process as "broken" in January, citing "systematic failures at the agency."

The inspector general for the State Department also released a report criticizing the agency's public records process in January. The report highlighted failures in the executive secretary's office, which responds to records requests for the Office of the Secretary.

Since last fall, the State Department has taken additional steps to increase transparency, recently hiring a transparency coordinator.

But the late discovery of the electronic folders has set back the release of information in a number of public records lawsuits filed against the State Department by watchdog groups.

The State Department first disclosed that staffers had discovered the unsearched folders in a January court filing. Attorneys for the department asked the court for additional time to process and release the documents in response to a 2014 lawsuit filed by the government ethics group Judicial Watch.

Around the same time, the State Department alerted the House Select Committee on Benghazi to the discovery. On April 8, the department turned over 1,100 pages of documents from the electronic folders to the House Benghazi Committee, over a year after the committee's subpoena. The committee had received other documents from the production in February.