A former CIA high-value detainee, who provided bogus information that was cited by the Bush administration in the run-up to the Iraq war, has died in a Libyan prison, an apparent suicide, according to a Libyan newspaper.

A researcher for Human Rights Watch, who met Ibn al-Sheikh al-Libi at the Abu Salim prison in Tripoli late last month, said a contact in Libya had confirmed the death.

Libi was captured fleeing Afghanistan in late 2001, and he vanished into the secret detention system run by the Bush administration. He became the unnamed source, according to Senate investigators, behind Bush administration claims in 2002 and 2003 that Iraq had provided training in chemical and biological weapons to al-Qaeda operatives. The claim was most famously delivered by then-Secretary of State Colin L. Powell in his address to the United Nations in February 2003.

Powell later called the speech a "blot" on his record, saying he was not given all available intelligence and analysis within the government. The Defense Intelligence Agency and some analysts at the CIA had questioned the veracity of Libi's testimony, which was obtained after the prisoner was transferred to Egyptian custody for questioning by the CIA, according to Senate investigators.

In their book "Hubris: The Inside Story of Spin, Scandal, and the Selling of the Iraq War," Michael Isikoff and David Corn said Libi made up the story about Iraqi training after he was beaten and subjected to a "mock burial" by his Egyptian interrogators, who put him in a cramped box for 17 hours. Libi recanted the story after being returned to CIA custody in 2004.

When President George W. Bush ordered the 2006 transfer to Guantanamo Bay, Cuba, of high-value detainees previously held in CIA custody, Libi was pointedly missing. Human rights groups had long suspected that Libi was instead transferred to Libya, but the CIA had never confirmed where he was sent.

"I would speculate that he was missing because he was such an embarrassment to the Bush administration," said Tom Malinowski, the head of the Washington office of Human Rights Watch. "He was Exhibit A in the narrative that tortured confessions contributed to the massive intelligence failure that preceded the Iraq war."

The first independent confirmation of Libi's whereabouts came two weeks ago. Heba Morayef, a researcher for Human Rights Watch, said she and a colleague met him briefly in a courtyard at the Abu Salim prison on April 27. The two were there to examine the treatment of prisoners in Libya, including other detainees once held by the United States.

Libi angrily rejected speaking to the researchers, saying, "Where were you when I was being tortured in American prisons?" according to Morayef, who described the encounter in a phone interview.

The Libyan newspaper Oed reported Sunday that Libi was found dead in his cell after killing himself, but added that friends of the 46-year-old former preacher, who ran a terrorist training camp in Afghanistan, questioned the alleged cause of death.

The Libyan government has not confirmed the death, and the Libyan Embassy in Washington said it had no information. The CIA also declined to comment.

Human Rights Watch called for an independent investigation of the death.

Libi was among dozens of former "ghost prisoners" who were in American custody overseas but whose disposition has never been officially released, according to human rights groups and a recently leaked report by the International Committee of the Red Cross. Most of these former detainees are believed to have been returned to their home countries, including to states such as Syria.

The Obama administration recently announced that it was decommissioning the CIA's global network of secret prisons, which have been mothballed since 2006, but human rights activists say the U.S. government should still provide the ICRC with an accounting of where it sent every prisoner it once held.

Staff researcher Julie Tate contributed to this report.