In the early years after Sept. 11, 2001, the CIA turned some Guantanamo Bay prisoners into double agents, sending them home to help the United States kill terrorists, current and former U.S. officials said.

The CIA promised the prisoners freedom, safety for their families and millions of dollars from the agency’s secret accounts.

It was a gamble. Officials knew there was a chance that some prisoners might quickly spurn their deal and kill Americans.

The program was carried out in a secret facility: eight small cottages a few hundred yards from the administrative offices of the prison at Guantanamo Bay, Cuba. The cottages, hidden behind a ridge covered in thick scrub and cactus, were designed to feel more like hotel rooms than prison cells, and some CIA officials jokingly referred to them collectively as the Marriott.

The program and the handful of men who passed through had various official CIA code names. But those who were aware of the cluster of cottages knew it best by its sobriquet: Penny Lane.

This satellite image provided by and DigitalGlobe, captured on Sept. 2, 2010, shows a portion of Naval Station Guantanamo Bay, Cuba, including the secret facility known as Penny Lane, upper middle in white. (AP)

It was a nod to the classic Beatles song and a riff on the CIA’s other secret facility at Guantanamo Bay, a prison known as Strawberry Fields.

Nearly a dozen current and former U.S. officials described aspects of the program to the Associated Press. All spoke on the condition of anonymity because they were not authorized to discuss the secret program publicly by name, even though it ended in about 2006.

Some of the men who passed through Penny Lane helped the CIA find and kill many top al-Qaeda operatives, current and former officials said. Others stopped providing useful information, and the agency lost touch with them.

Current and former officials said dozens of prisoners were evaluated, but only a handful, from a variety of countries, were turned into spies who signed agreements to work for the CIA.

Agency spokesman Dean Boyd declined to comment.

The U.S. government says it has confirmed that about 16 percent of former Guantanamo Bay detainees rejoined the fight against the United States. Officials suspect but have not confirmed that 12 percent more rejoined.

It’s not clear whether the men from Penny Lane are included in those figures. But because only a small number of people went through the program, it probably would not change the figures significantly either way. None of the officials interviewed by the AP knew of an instance in which any double agent killed Americans.

Infiltrating al-Qaeda has been one of the CIA’s most sought-after but difficult goals, one that other foreign intelligence services have only occasionally accomplished. Candidates for Penny Lane needed legitimate terrorist connections; to be valuable to the CIA, the men had to be able to reconnect with al-Qaeda.

Prisoners agreed to cooperate for a variety of reasons, officials said. Some received assurances that the United States would resettle their families. One detainee thought al-Qaeda had perverted Islam and believed that it was his duty as a Muslim to help the CIA destroy it. Another agreed to cooperate after the agency insinuated that it would harm his children, a former official said, a threat similar to those interrogators made to self-proclaimed Sept. 11 mastermind Khalid Sheik Mohammed.

All were promised money. Exactly how much each received remains unclear. But altogether, the government paid millions for their services, officials said. The money came from a secret CIA account, code-named Pledge, that is used to pay informants, officials said.

Al-Qaeda suspected that the CIA would attempt a program like this, and its operatives have been very suspicious of former Guantanamo Bay detainees, intelligence officials and experts said. In one case, a former official recalled, al-Qaeda came close to discovering a double agent in its midst.

The U.S. government had such high hopes for Penny Lane that one former intelligence official recalled discussions about whether to secretly release two Pakistani men into the United States on student or business visas. The hope was that they would connect with al-Qaeda and lead authorities to members of a U.S. cell.

Another former senior intelligence official said that never happened.

Officials said the program ended in 2006 as the flow of detainees to Guantanamo Bay slowed to a trickle. The last prisoner arrived there in 2008.

— Associated Press