The voices of former detainees tortured by the CIA at secret overseas prisons are revealed in newly declassified transcripts of hearings held at Guantanamo Bay, Cuba, after the men were transferred there in 2006.

In the case of Zayn al-Abidin Muhammed Hussein, a Saudi-born Palestinian better known as Abu Zubaida, who was arrested in 2002 and is still held at the U.S. military prison at Guantanamo Bay, CIA interrogators supposedly apologized to him after the agency realized it had overestimated his role in al-Qaeda. The CIA believed he was a senior figure in the terrorist organization when he was, in fact, a kind of fixer in Pakistan who helped people travel to training camps in Afghanistan.

Abu Zubaida was the first detainee to be waterboarded by the CIA and was subjected to the procedure 83 times while held at a facility in Thailand.

“After that, all they said to me was, ‘Sorry, we made a big mistake,’ ” Abu Zubaida said at a military hearing at Guantanamo Bay.

Abu Zubaida said that while in CIA custody, he was beaten, prevented from using the bathroom for up to 36 hours at a time, and forced to relieve himself in a room with barely enough space for him and a bucket. He could only stand or sit on the bucket filled with his urine, he said.

“They didn’t care that I almost died from these injuries,” he said. “Doctors told me that I nearly died four times.”

Abu Zubaida said he falsified knowledge about terrorist plots in an effort to make the abuse stop.

The government released the transcripts this week in a response to a Freedom of Information lawsuit brought by the American Civil Liberties Union, and they were first reported on by the New York Times. All the documents stem from a series of hearings held at Guantanamo Bay in 2007. Abu Zubaida and other “high-value” detainees are held in a top-secret facility at the base that is separate from the camps that hold the bulk of the remaining 80 detainees.

The hearings, known as Combatant Status Review Tribunals, include statements from six prisoners including Khalid Sheik Mohammed, the self-proclaimed mastermind of the Sept. 11, 2001, attacks, and Abd al-Rahim al-Nashiri, who is accused of being involved in the 2000 attack on the USS Cole in Yemen.

The release of the tribunal transcripts adds to a growing body of public knowledge about the CIA’s interrogation program, including the long executive summary of a 2014 Senate Intelligence Committee report and a series of redacted 2009 transcripts of hearings with the detainees.

On Wednesday, the CIA also posted 50 other documents related to the program. Among them is a memo recounting a meeting on Nov. 8, 2006, that CIA officials had with the International Committee of the Red Cross. Then-CIA General Counsel John A. Rizzo noted that “as described to us, albeit in summary form, what the detainees allege actually does not sound that far removed from reality.”

Supporters of the CIA’s interrogation methods after 9/11 have argued that they saved lives, while critics, including the authors of the Senate report, have said the most actionable information came from regular interrogation techniques or other sources.

Nashiri said he was hung by the arms from the ceiling for almost a month, according to the transcripts. After that, he said, he was placed in a “half meter by half meter” box for a week.

“I used to be able to run about 10 kilometers,” Nashiri said. “Now I cannot walk for more than 10 minutes. My nerves are swollen in my body.”

He added: “These things happen for more than two years. That thing did not stop until here. So many things happened.”