Four detainees held for more than a decade at the U.S. military detention center at Guantanamo Bay, Cuba, have been transferred to Afghanistan, the Pentagon announced Saturday.

The Afghan detainees were released late Friday at the request of Afghan President Ashraf Ghani — an indication, one senior administration official said, “of the confidence we have in the new government” in Kabul. Ghani’s request, the official added, was made in October, shortly after he was sworn into office.

The United States and Afghanistan have not started serious discussions about repatriating the remaining eight Afghans still held at Guantanamo Bay, said the official, speaking on the condition of anonymity because of the sensitivity of the transfers.

The Obama administration has moved aggressively this year to reduce the detainee population at Guantanamo, hoping to fulfill President Obama’s pledge to close the site despite congressional resistance.

The administration has transferred a total of 23 detainees this year, leaving 132 remaining. More are expected to be transferred before year’s end. Of the remaining detainees, 64 have been cleared for transfer.

The countries that have accepted detainees this year have included Uruguay, Slovakia, Georgia, Saudi Arabia, Algeria and Kuwait. Five other detainees were sent to Qatar as part of a deal to free Army Sgt. Bowe Bergdahl, who was captured in Afghanistan in 2009.

The newly released Afghans were identified as Mohammed Zahir, Abdul Ghani, Khi Ali Gul and Shawali Khan. All four were approved for transfer after the administration carefully reviewed their backgrounds to assess any security threat they might pose in the future, officials said.

One of them, Zahir, “was arrested on suspicion of possessing weapons including Stinger missiles and uranium, which detainee’s recovered documents indicate was intended for use in a nuclear device,” according to U.S. military files disclosed by the anti-secrecy group WikiLeaks.

The files say that Gul “planned and executed attacks against U.S. and Coalition forces.” Khan was accused of carrying out “terrorist operations,” while Ghani “has admitted he was involved in at least one rocket attack on U.S. forces at the Kandahar” airport in 2002, the files assert.

A second senior U.S. official familiar with the cases said “most, if not all, of these accusations have been discarded.”

“Each of these four individuals, at worst, could be described as low-level, if that,” the official said.

Officials have said much of the information collected in the files of some detainees ultimately proved to be inaccurate.

Correction: An earlier version of this story had an incorrect number of prisoners released this year.