WASHINGTON, Oct. 16 - Many detainees at Guantánamo Bay were regularly subjected to harsh and coercive treatment, several people who worked in the prison said in recent interviews, despite longstanding assertions by military officials that such treatment had not occurred except in some isolated cases.
The people, military guards, intelligence agents and others, described in interviews with The New York Times a range of procedures that included treatment they said was highly abusive occurring over a long period of time, as well as rewards for prisoners who cooperated with interrogators.
One regular procedure that was described by people who worked at Camp Delta, the main prison facility at the naval base in Cuba, was making uncooperative prisoners strip to their underwear, having them sit in a chair while shackled hand and foot to a bolt in the floor, and forcing them to endure strobe lights and screamingly loud rock and rap music played through two close loudspeakers, while the air-conditioning was turned up to maximum levels, said one military official who witnessed the procedure. The official said that was intended to make the detainees uncomfortable, as they were accustomed to high temperatures both in their native countries and their cells.
Such sessions could last up to 14 hours with breaks, said the official, who described the treatment after being contacted by The Times.
"It fried them,'' the official said, who said that anger over the treatment the prisoners endured was the reason for speaking with a reporter. Another person familiar with the procedure who was contacted by The Times said: "They were very wobbly. They came back to their cells and were just completely out of it.''
The new information comes from a number of people, some of whom witnessed or participated in the techniques and others who were in a position to know the details of the operation and corroborate their accounts.
Those who spoke of the interrogation practices at the naval base did so under the condition that their identities not be revealed. While some said it was because they remained on active duty, they all said that being publicly identified would endanger their futures. Although some former prisoners have said they saw and experienced mistreatment at Guantánamo, this is the first time that people who worked there have provided detailed accounts of some interrogation procedures.
One intelligence official said most of the intense interrogation was focused on a group of detainees known as the "Dirty 30'' and believed to be the best potential sources of information.
In August, a report commissioned by Defense Secretary Donald H. Rumsfeld found that tough techniques approved by the government were rarely used, but the sources described a broader pattern that went beyond even the aggressive techniques that were permissible.
The issue of what were permissible interrogation techniques has produced a vigorous debate within the government that burst into the open with reports of abuses at Abu Ghraib prison in Baghdad and is now the subject of several investigations.
Since the Sept. 11 attacks and the war in Afghanistan, the administration has wrestled with the issue of what techniques are permissible, with many arguing that the campaign against terrorism should entitle them to greater leeway. Alberto R. Gonzales, the White House counsel said, for example, in one memorandum that the Geneva Conventions were "quaint" and not suitable for the war against terrorism.
David Sheffer, a senior State Department human rights official in the Clinton administration who teaches law at George Washington University, said the procedure of shackling prisoners to the floor in a state of undress while playing loud music - the Guantánamo sources said it included the bands Limp Bizkit and Rage Against the Machine, and the rapper Eminem - and lights clearly constituted torture. "I don't think there's any question that treatment of that character satisfies the severe pain and suffering requirement, be it physical or mental, that is provided for in the Convention Against Torture,'' Mr. Sheffer said.
Pentagon officials would not comment on the details of the allegations. Lt. Cmdr. Alvin Plexico issued a Defense Department statement in response to questions, saying that the military was providing a "safe, humane and professional detention operation at Guantánamo that is providing valuable information in the war on terrorism.''
The statement said: "Guantánamo guards provide an environment that is stable, secure, safe and humane. And it is that environment that sets the conditions for interrogators to work successfully and to gain valuable information from detainees because they have built a relationship of trust, not fear.''
The sources portrayed a system of punishment and reward, with prisoners who were favored for their cooperation with interrogators given the privilege of spending time in a large room nicknamed "the love shack'' by the guards. In that room, they were free to relax and had access to magazines, books, a television and a video player and some R-rated movies, along with the use of a water pipe to smoke aromatic tobaccos. They were also occasionally given milkshakes and hamburgers from the McDonald's on the base.
The Pentagon said the information gathered from the detainees "has undoubtedly saved the lives of our soldiers in the field,'' adding: "And that information also saves the lives of innocent civilians at home and abroad. At Guantánamo we are holding and interrogating people that are a clear danger to the U.S. and our allies and they are providing valuable information in the war on terrorism.''
Although many critics of the detentions at Guantánamo have said that the majority of the roughly 590 inmates are low-level fighters who have little intelligence to impart, Pentagon and intelligence officials have insisted that the facility houses many dangerous veteran terrorists and officials of Al Qaeda.
The intelligence official said that many of those imprisoned at Guantánamo had valuable information but that it was not always clear what their standing in Al Qaeda was. The official said the first four detainees now facing war crimes charges before a military tribunal at the base were specifically chosen because they had not been harshly treated and therefore would be less likely to make any embarrassing allegations.
The people who worked at the prison also described as common another procedure in which an inmate was awakened, subjected to an interrogation in a facility known as the Gold Building, then returned to a different cell. As soon as the guards determined the inmate had fallen into a deep sleep, he was awakened again for interrogation after which he would be returned to yet a different cell. This could happen five or six times during a night, they said.
Much of the harsh treatment described by the sources was said to have occurred as recently as the early months of this year. After the scandal about mistreatment of prisoners at the Abu Ghraib prison in Iraq became public in April, all harsh techniques were abruptly suspended, they said.
The new accounts of mistreatment at Guantánamo provide fresh evidence about how practices there may have contributed to the abuses at Abu Ghraib. One independent military panel said in a report that the approach used at Guantánamo had "migrated to Abu Ghraib.
The vigorous debate within the administration about what techniques were permissible in interrogations was set off when the Justice Department provided a series of memorandums to the White House and Defense Department providing narrow definitions of torture. In February 2002, Mr. Bush ordered that the prisoners at Guantánamo be treated "humanely and, to the extent appropriate with military necessity, in a manner consistent with'' the Geneva Conventions.
In March 2002, a team of administration lawyers accepted the Justice Department's view, concluding in a memorandum that President Bush was not bound by either the Convention Against Torture or a federal antitorture statute because he had the authority to protect the nation from terrorism. When some of the memorandums were disclosed, the administration tried to distance itself from the rationale for the harsher treatment.
At the request of military intelligence officials who complained of tenacious resistance by some subjects, Mr. Rumsfeld approved a list of 16 techniques for use at Guantánamo in addition to the 17 methods in the Army Field Manual in December 2002. But he suspended those approvals in January 2003 after some military lawyers complained they were excessive and possibly unlawful.
In April 2003, after a review, Mr. Rumsfeld issued a final policy approving of 24 techniques, some of which needed his permission to be used.
But the approved techniques did not explicitly cover some that were used, according to the new accounts. The only time that using loud music and lights seems to appear in the documents, for example, is as a proposal that seems never to have been adopted. The April 16 memorandum allows interrogators to place a detainee "in a setting that may be less comfortable'' but should not "constitute a substantial change in environmental quality.''
Officials said the guards' patience was often stretched, especially when inmates threw human waste at the military police officers, a frequent occurrence. The guards, for their part, had their own tricks, including replacing the prayer oil in little bottles given to the inmates with a caustic pine-smelling floor cleaner.
An August 2004 report by a panel headed by James R. Schlesinger, the former defense secretary, said the harsher approved techniques on Mr. Rumsfeld's list were used on only two occasions. In addition, the report said, there were about eight abuses by guards at Guantánamo that occurred and were investigated.
In guided tours of Guantánamo provided to the news media and members of Congress, the military authorities contended that the system of rewards and punishments affected only issues like whether the inmates could be deprived of books, blankets and toilet articles. The interrogation sessions themselves, the officials consistently said, did not employ any harsh treatment but were devised only to build a trusting relationship between the interrogator and the detainee.