A suspected Iraqi member of the terrorist group Al Ansar, whom CIA Director George J. Tenet asked Defense Secretary Donald H. Rumsfeld to hide off the official registry of prisoners, became lost in the system for seven months and was not interrogated by CIA or military officials during that time, Pentagon and intelligence officials said yesterday.

In his report on abuses at the Abu Ghraib prison, Army Maj Gen. Antonio M. Taguba criticized the CIA practice of maintaining "ghost detainees" -- prisoners who were not officially registered and were moved around to hide them from Red Cross teams. Taguba called the practice "deceptive, contrary to Army doctrine and in violation of international law."

The man was picked up by the Kurdish military in June or July 2003 and taken outside Iraq by the CIA. He was interrogated under secret authority to treat people believed to be involved in the insurgency against U.S. troops differently than others, a U.S. intelligence official said.

President Bush has said the Geneva Conventions apply to all combatants in Iraq. The conventions require that enemy prisoners be registered, be allowed visits by international organizations and not be taken to third countries.

In May, as part of an overall review of detention problems in Iraq, the man's status made its way to the Pentagon. "It was obviously apparent this was an issue that needed to be resolved," said Pentagon spokesman Bryan Whitman. The man is to soon get an internee number.

This is the first known case in which Tenet and Rumsfeld were said to be involved in such an arrangement. In October, the CIA general counsel's office told the agency it had to return the captive to Iraq. It was then that Tenet asked Rumsfeld not to give the prisoner a number and to hide him because the CIA wanted to further interrogate him, Whitman said.

The CIA forgot about the man until January, when CIA officers inquired of his whereabouts at Camp Cropper, where he was being held. Because he had not been assigned a number and no official records were kept, the military prison officials responded that they could not find him, intelligence officials said.

Twice after that, however, military prison officials began inquiring about the man's status. "When the request was made from the command in Iraq, it was not handled through the channels that could have resolved it," said Whitman, and the man languished for several more months. His status was first reported by U.S. News & World Report.

Meanwhile, a Pentagon spokesman said yesterday that Gen. Paul J. Kern will now head the investigation that has focused on the role of military intelligence personnel in abuse of detainees at Abu Ghraib, where military police and intelligence soldiers were photographed humiliating and assaulting prisoners.

Seven MPs have been charged with the abuses.

While the investigation was spurred by shocking photographs allegedly taken by low-ranking soldiers, the investigation has since been climbing the military chain of command. Documents obtained by The Washington Post show that higher-ranking officers approved a range of severe interrogation tactics used at the prison, including using military dogs to threaten detainees.

Maj. Gen. George R. Fay -- a two-star general -- has been investigating the abuses over recent weeks, but his team was limited to questioning officials only at his rank and below. Documents show that Lt. Gen. Ricardo S. Sanchez, commander of U.S. troops in Iraq and initial overseer of the abuse investigation, had to give approval for some interrogation techniques to be used. As a three-star general, Sanchez had been out of the investigation's reach.

Last week, Sanchez removed himself from the investigation and asked the Pentagon to appoint a higher-ranking officer to take responsibility. That cleared the way for investigators to question Sanchez, who has said he did not sanction maltreatment and did not know about abuse of prisoners until January, when a soldier turned in photographs documenting it.

Since late 2001, Kern has been in charge of the Army Materiel Command, which provides technology, acquisition support and logistics to the Army worldwide. Kern has also commanded the 4th Infantry Division and has worked as the senior military assistant to the secretary of defense.

Gen. Peter J. Schoomaker told reporters earlier this week that he expected a four-star would be named to head the abuse investigation.