Human Rights Watch says it has uncovered evidence suggesting that the Bush administration covered up the extent of waterboarding at secret CIA prisons early in the war on terrorism. Officials have long maintained that only three key al Qaeda suspects were subjected to the harsh interrogation technique, which has been widely condemned as torture. But now, Human Rights Watch investigators say they have found two Libyan Islamists who were subjected to similar treatment nine years ago in Afghanistan, before being returned home and imprisoned by Moammar Gadhafi. Was waterboarding more widespread than U.S. officials acknowledge? Here, a brief guide:

What does Human Rights Watch say, exactly?

Researcher Laura Pitter talked to 14 Libyans who say they were held by the U.S. and then later returned to Libya. While in U.S. custody, they say they were subjected to harsh treatment, such as being stripped naked and chained, and being contorted into painful stress positions. Two of the men — Mohammed Shoroeiya and Khalid al-Sharif — described another technique that fit the description of waterboarding, although they didn't use the term. "They start to pour water to the point where you feel like you are suffocating," Shoroeiya said. "They wouldn't stop until they got some kind of answer from me."

Who are these men?

Most of them were members of the Libyan Islamic Fighting Group, which was dedicated to overthrowing Gadhafi. They had fled Gadhafi's Libya, and their group was running training camps in Afghanistan during the years when al Qaeda was using the country as its base. The Libyans say they had no ties to al Qaeda — they were focused on Gadhafi, not the U.S. — but were swept up in the American hunt for terrorists in the aftermath of the Sept. 11, 2001, terrorist attacks. The Libyan Islamic Fighting Group later joined Libya's revolution, and since Gadhafi's fall, the former detainees have lived freely in Libya. Al-Sharif is now head of the country's National Guard.

Why is their story only coming to light now?

None of the men went looking to tell their story, Pitter says. Their names were found in documents discovered at Libya's intelligence headquarters after Gadhafi's regime fell, and Pitter tracked them down.

How has the CIA responded?

CIA spokeswoman Jennifer Youngblood said she couldn't address the cases cited in the Human Rights Watch report, but reiterated previous U.S. statements that the only confirmed cases of waterboarding were those of Khalid Shaikh Mohammed, organizer of the Sept. 11 attacks, and two other al Qaeda suspects — none of them Libyans. "The agency has been on the record that there are three substantiated cases in which detainees were subjected to the waterboarding technique," she says.

Sources: CBC, Guardian, New York Daily News, New York Times, NPR