The U.S. government has charged a federal contractor with the theft of government property and removal of classified materials, including multiple top secret documents that would pose a threat to U.S. security if disclosed, the Justice Department said Wednesday.

The government produced the documents through "sensitive sources, methods and capabilities," and revealing the documents would expose those methods, the Justice Department said in a statement.

Harold Thomas Martin of Glen Burnie, Md., was arrested on Aug. 27 but his case is only being made public today, NPR's Carrie Johnson reports.

"U.S. law enforcement kept the case under wraps for weeks as it investigated his actions," Carrie says. "Martin, who worked for the government contractor Booz Allen Hamilton, allegedly told agents he knew what he had done was wrong."

A Booz Allen spokesman says Martin has been fired and that the company is cooperating with the FBI. A law enforcement source tells Carrie that Martin was doing work as a government contractor for the National Security Agency while employed at Booz Allen.

Public defenders representing Martin tell Carrie that he is a Navy veteran who "devoted most of his career to protecting our country." Here's their full statement:

"Harold Martin has now been charged in federal court. This is the beginning of a long and important process. These are mere allegations. We have seen no evidence yet. There is no evidence that Mr Martin intended to betray his country. We do know that Mr Martin loves his family and America. He served his country honorably as a lieutenant in the United States Navy. He has devoted most of his career to protecting our country. We look forward to defending Hal Martin in court."

The Justice Department says Martin had top secret security clearance. A search of his house, car and two storage sheds found both hard-copy and digital documents that were property of the U.S. government, including classified documents, the department alleges. More than $1,000 worth of stolen government property was also uncovered, the department says.

The announcement from the Justice Department highlights six documents in particular:

"The complaint alleges that among the classified documents found in the search were six classified documents obtained from sensitive intelligence and produced by a government agency in 2014. These documents were produced through sensitive government sources, methods and capabilities, which are critical to a wide variety of national security issues. The disclosure of the documents would reveal those sensitive sources, methods and capabilities.

"The documents have been reviewed by a person designated as an original classification authority, and in each instance, the authority has determined that the documents are currently and properly classified as Top Secret, meaning that unauthorized disclosure reasonably could be expected to cause exceptionally grave damage to the national security of the U.S."

The charges against Martin carry a maximum sentence of one year in prison for the classified documents, and 10 years in prison for the theft of property.

The New York Times,citing law enforcement and intelligence officials, reports the documents could contain "highly classified computer codes developed to hack into the networks of foreign governments."

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