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CNN  — 

A retired Air Force lieutenant colonel who stored files with classified information at his Florida home is set to plead guilty in February to one count of unlawful retention of national defense information, according to court documents.

The defendant, Robert Birchum, served in the Air Force for more than 30 years and previously held top secret clearance. According to his plea agreement, he stored hundreds of files that contained information marked as top secret, secret or confidential classified outside of authorized locations.

In 2017, investigators found a thumb drive, two hard drives and paper documents containing classified information in Birchum’s possession, including at his home, court documents state. Two of the files on the thumb drive at Birchum’s home contained information on the National Security Agency’s “methods of collection, and identify targets’ vulnerabilities,” according to the plea.

CNN has reached out to Birchum’s attorney for comment.

A plea hearing is set for February 21 in a district court in Florida, and he faces a maximum of 10 years in prison.

The Daily Beast first reported on the plea agreement.

The case comes to a close as Washington is embroiled in controversy over the handling of classified documents by President Joe Biden, former President Donald Trump and former Vice President Mike Pence. Two special counsels are investigating Biden and Trump, and the Justice Department is reviewing the Pence case.

While Birchum had top secret clearance through his various positions in the Air Force, including as an Intelligence Officer, “(t)he defendant’s residence was not a location authorized to store classified information, and the defendant knew as much,” the plea agreement states.

On a hard drive at his home, investigators found 10 files that had “information marked as Secret,” according to the agreement, as well as 48 paper documents that also contained information marked as secret. On the thumb drive recovered from his home, investigators say they found 135 files marked as containing classified information.

Separately, in a temporary residence overseas outside of a designated sensitive compartmented information facility (SCIF), investigators say they found another hard drive containing 117 files with classified national defense information.

According to court filings, Birchum retired from the Air Force in 2018. An Air Force spokesperson declined to comment.