The officials, who asked not to be identified, said the military transport with several dozen shackled detainees was expected to arrive at the base later in the day.
There are a total of 331 Afghan war captives at the base after 32 were flown in Wednesday. One of the 300 prisoners held before Wednesday's flight arrived was sent back to Afghanistan because of mental problems, one official said.
None of the nearly 200 captives still being held by the U.S. military in Afghanistan or the detainees in Guantanamo Bay has been charged with crimes, although the Pentagon has left open the possibility that at least some will face military trials authorized by President Bush in connection with Sept. 11 attacks on America.
Many of the detainees in Afghanistan are expected to be transferred to Cuba.
The Guantanamo detainees are now being held at Camp Delta, the new jail at the remote American base in southeastern Cuba. Transfers of captives from the Afghanistan war theater to the base were halted in mid-February when the base's controversial open air, chain-link cellblock known as Camp X-Ray was filled to capacity.
The temporary prison quickly became a symbol to human rights activists, who criticized the United States' stance that the captives are not prisoners of war under the Geneva conventions and questioned whether the U.S. military was committing human rights violations.
The military task force running the prison camp last — Monday completed the transfer of all 300 detainees from their chain-link cells to the more permanent prison made of solid cells in rows that look like long mobile homes. The new cells have wash basins with running water and flush toilets.
Officials at Guantanamo said the new prison is prepared to accept more detainees, with 76 empty units ready to be occupied and 204 under construction and set for completion by the end of May.
Like X-Ray, Camp Delta is surrounded by fences topped with razor wire and ringed by wooden guard towers manned by sharpshooters. But the new camp is enclosed inside a green mesh curtain, which prevents visitors from seeing in and keeps the prisoners from seeing the tightly guarded shoreline nearby.