WASHINGTON — The CIA’s use of harsh interrogation techniques on foreign terror suspects — a practice that has provoked international condemnation — was more widespread than the agency has publicly acknowledged, Senate investigators have learned.

Moreover, the CIA’s own internal documents confirm the agency’s culpability in the hypothermia death of one Afghan captive — an incident that also has never even been publicly discussed, McClatchy was told.

The new details were gathered as part of the Senate Intelligence Committee’s $40 million investigation of the agency’s now defunct interrogation and detention program. McClatchy’s sources, who included one former and one current U.S. official, spoke on the condition of anonymity because the information is classified.

Since the inception of the interrogation program shortly after the Sept. 11, 2001, terror attacks, the CIA has steadfastly refused to completely describe what happened to the estimated 100 detainees believed to be in its custody.

The committee is scheduled to vote Thursday on what is expected to be a damning 6,000-page report on the CIA practices that Sen. Dianne Feinstein, the committee’s chairwoman, has called “un-American and brutal.”

In a statement Tuesday night, CIA spokesman Dean Boyd said: “The CIA has not been provided with a final copy of the Senate Select Committee on Intelligence’s report on the former Rendition Detention and Interrogation (RDI) program and until we’re given the opportunity to review it, we are unable to comment on details it may contain. If portions of the report are submitted to the CIA for classification review, the CIA will carry out the review expeditiously.”

For the last six years, the CIA has maintained that only 30 detainees experienced such so-called enhanced interrogation techniques, and only three detainees were waterboarded, a form of simulated drowning that was deemed to be the most aggressive form of treatment authorized by the administration of President George W. Bush.

McClatchy’s sources differed somewhat on the actual number of detainees who endured the techniques, which included sleep deprivation, stress positions, being placed in small boxes and hearing loud music. One former U.S. official said a majority of the 100 detainees were subjected to the various tactics and confirmed the CIA’s account that only three were waterboarded. Another current official said it was not accurate to say that virtually all of the detainees were subjected to the techniques but described their use as “widespread.”

Most lawmakers and those familiar with the report agree on this much: “There will be a lot of things in those sections that will be upsetting to people to read,” said the former U.S. official. “But it would make it impossible for the United States to argue that this was defensible.

“There has to be certain levels of sunlight. The CIA and others are still saying these things were necessary and they had good results. But the public needs to know the horrific things that were done. What needs to be known is that these activities did not yield good and actionable and timely intelligence and they’re reprehensible by our own values and they cannot and must not be repeated.”

In its official response, the CIA has disputed some of the committee’s key findings.

In the case of the death of Gul Rahman, an Afghan who was shackled, doused with cold water and left in a cold cell partially clothed until he died of hypothermia, the CIA’s internal documents reviewed by the Senate confirm the agency’s culpability, the two sources said. Rahman died at a secret detention facility in Afghanistan known as the Salt Pit. His identity was kept secret for seven years.

Although news reports have cited anonymous sources who described how the agency may have tried keep the incident “off the books”, the committee had access to documents that confirmed the CIA may have tried to “minimize or sanitize that case.”

“The documents initially make it seem like it was an accident,” said the former official. “However, evidence pointed to what it actually was: willful negligence or even negligent homicide.”

McClatchy’s other source, however, cautioned that “this depends on how you look at it” because it could still characterized as an accident.

“This is formal confirmation,” said one source. “The way the (enhanced interrogation techniques) were applied were horrifying. If everything in that report were to be known publicly there would be a real concern about a reinvigorated terrorist threat against us.”

The 15-member committee, seven Democrats, seven Republicans and Sen. Angus King, a Maine independent who caucuses with Democrats, is expected to vote Thursday on whether to send the executive summary and the report’s findings to be declassified.

The summary was still being reviewed for possible redactions. If approved by the committee, it would then go to President Barack Obama, who would decide what to release publicly.

The outcome of the vote remains uncertain. King is expected to reveal Wednesday how he will vote; if all Democrats agree to release, that would provide a majority. Republicans have been wary of the report, with some saying it is exaggerated and contains errors.

Some Republicans are discussing releasing their own views when a majority report is released.

“It would list specifically where it’s wrong and why it’s wrong,” said Sen. Tom Coburn, R-Okla.

But others familiar with the report countered that the evidence will speak for itself.

“If the CIA rebuttal is published it would be seen for what it really is: a political cover. I think they even realize that if they publish it alongside the report it will make them look bad and maybe even worse because it denies reality.”

Four other detainees are believed to have died in CIA custody, including Manadal al Jamadi, who reportedly died after he was hung in a crucifixion-like pose and his head had been covered with a plastic bag.

Although the CIA’s former inspector general referred nine cases to federal prosecutors during the Bush administration, only one CIA contractor ended up being prosecuted.

During the Obama administration, a new investigation was launched into two of the deaths, including Rahman. The Justice Department later declined to prosecute.