Nine prisoners from Guantanamo Bay have been released and sent to Saudi Arabia for resettlement, the Defense Department announced Saturday.

All nine are Yemeni but have family ties to Saudi Arabia. None of the men had been charged and all but one had been cleared for release from the U.S. base in Cuba since at least 2010. One was approved for release by a review board last year.

They could not be sent to their homeland because of instability there.

The prisoners include a frequent hunger striker whose weight had dropped to as low as 74 pounds (34 kilograms) at one point.

The interagency Guantanamo Review Task Force reviewed the cases of all nine prisoners, unanimously approving eight for transfer. The ninth was later approved by another government review board.

"In accordance with statutory requirements, the secretary of defense informed Congress of the United States' intent to transfer these individuals and of the secretary's determination that these transfers meet the statutory standard," the Defense Department said in a statement.

"The United States is grateful to the government of the Kingdom of Saudi Arabia for its humanitarian gesture and willingness to support ongoing U.S. efforts to close the Guantanamo Bay detention facility," the statement read.

The release announced Saturday in a Pentagon statement brings the Guantanamo prisoner population to 80, including 26 cleared men expected to leave by the end of the summer.

Fox News' Lucas Tomlinson and The Associated Press contributed to this report.