The Central Intelligence Agency will begin recalling furloughed civilian workers needed to carry out the spy agency’s core missions today, according to CIA Director John Brennan.

Businessweek reports that not all CIA civilian employees will return to work, but only those “necessary to carry out CIA’s core missions of foreign intelligence collection, all-source analysis, covert action, and counterintelligence,” an email from Brennan said.

Brennan also remarked in the email that keeping staffing at its current dramatically reduced level “would pose a threat to the safety of human life and the protection of property.”

The Director of National Intelligence James Clapper has authorized a similar recall in his office, as well as at the National Counterterrorism Center, the National Counterproliferation Center, the Office of the National Counterintelligence Executive and the National Intelligence Council, the article reports.

More than 12,000 CIA employees have been furloughed, and one official said there were indications that some terrorist organizations and other hostile groups might be attempting to learn if they could take advantage of the temporary staffing cuts, which affected 72 percent of the U.S. intelligence workforce.

Defense Secretary Chuck Hagel recalled most of his department’s furloughed civilian employees on October 5, which helped to ease the burden on the Defense Intelligence Agency, the National Security Agency and the National Geospatial-Intelligence Agency.