More than 25 of the CIA's War on Terror prisoners were subjected to sleep deprivation for as long as 11 days at a time during the administration of former president George W. Bush, the Los Angeles Times reported.
At one stage, the CIA was allowed to keep prisoners awake for as long as 11 days, the Times reported, citing memoranda made public by the Justice department last month.
The limit was later reduced to just over a week, according to the report.
Sleep deprivation was one of the most important elements in the CIA's interrogation program, seen as more effective than more violent techniques used to help break the will of suspects.
Within the CIA, it was seen as having the advantage of eroding a prisoner's will without leaving lasting damage.
The technique is now prohibited by President Obama's ban on harsh interrogation methods issued in January, although a task force is reviewing its use along with other interrogation methods, the Times reported.
But details in the Justice Department memos released by Obama suggest that the method, which involved suspects standing for days on end, dressed only in a diaper and chained to the floor, was more controversial than previously known.
According to the memos, medical personnel were present to make sure prisoners weren't injured. But a 2007 Red Cross report on the CIA program said detainees' wrists and ankles bore scars from their shackles, the newspaper reported.