The program, which was carried out in a complex known as Penny Lane just a few hundred yards from the administrative offices at the prison, aided in the killing of “many” top al-Qaeda operatives, Associated Press reported on Tuesday.

The eight small cottages, seen in the satellite image above, were hidden behind a ridge covered in thick scrub and cactus. Unlike the prison next door, inside the motel-style complex detainees were treated to comfortable beds, private kitchens and a small patio.

The CIA offered the prisoners freedom, safety for their families and millions of dollars from the agency’s secret bank account, codenamed Pledge, in return for spying for the US.

Some of the information provided by the released detainees was used to launch Predator drone strikes, an official said, while other double agents ultimately stopped providing information and lost contact with the CIA.

Al-Qaeda apparently suspected the US may try to infiltrate the group with former Guantanamo detainees and was highly-skeptical of those who returned home. In one instance, an official recalled, the group came very close to discovering a double-agent.

Officials involved with the risky program, which ended in 2006, told the AP their greatest fear was that a former detainee would attack Americans then publicly reveal he was paid by the CIA. There were no known instances in which this occurred.

Barack Obama, the US president, promised during his first campaign for the White House in 2008 that he would close the Guantanamo Bay detention center, but he has failed to do so.

NTJ/BA