CIA interrogators used waterboarding, the near-drowning technique that top Obama administration officials have described as illegal torture, 266 times on two key prisoners from Al-Qaeda, far more than had been previously reported. The CIA officers used waterboarding at least 83 times in Aug. 2002 against Abu Zubaydah, according to a 2005 Justice Department legal memorandum. Abu Zubaydah has been described as a Qaeda operative, the New York Times reported A former CIA officer, John Kiriakou, told ABC News and other news media organizations in 2007 that Abu Zubaydah had undergone waterboarding for only 35 seconds before agreeing to tell everything he knew. The 2005 memo also says that the CIA used waterboarding 183 times in March 2003 against Khalid Shaikh Mohammed, the self-described planner of the Sept. 11, 2001, terrorist attacks. The New York Times reported in 2007 that Mohammed had been barraged more than 100 times with harsh interrogation methods, causing CIA officers to worry that they might have crossed legal limits and to halt his questioning. But the precise number and the exact nature of the interrogation method was not previously known. The release of the numbers is likely to become part of the debate about the morality and efficacy of interrogation methods that the Justice Department under the Bush administration declared legal even though the United States had historically treated them as torture. President Obama visited the Central Intelligence Agency headquarters Monday, a visit clearly designed to reassure the leadership and rank-and-file at the spy agency of his confidence despite having released a series of torture memos written and acted upon under his Republican predecessor. Obama has said CIA officers who had used waterboarding and other harsh interrogation methods with the approval of the Justice Department would not be prosecuted. He has repeatedly suggested that he opposes Congressional proposals for a “truth commission” to examine Bush administration counterterrorism programs, including interrogation and warrantless eavesdropping. The Senate Intelligence Committee has begun a yearlong, closed-door investigation of the CIA interrogation program, in part to assess claims of Bush administration officials that brutal treatment, including slamming prisoners into walls, shackling them in standing positions for days and confining them in small boxes, was necessary to get information. The fact that waterboarding was repeated so many times may raise questions about its effectiveness, as well as about assertions by Bush administration officials that their methods were used under strict guidelines. A footnote to another 2005 Justice Department memo released Thursday said waterboarding was used both more frequently and with a greater volume of water than the CIA rules permitted.