Defense Secretary Donald H. Rumsfeld's (search) panel investigating prisoner abuse interviewed the Pentagon's top civilian intelligence official Monday and more than a half dozen other senior defense officials and active duty personnel in Iraq.

In a statement, the panel confirmed it conducted more than a half dozen interviews and its chairman, former Defense Secretary James Schlesinger (search), vowed the members would "provide an unvarnished assessment of how these abuses happened."

The panel didn't identify the individuals it interviewed Monday. But an official familiar with the investigation said members met with the Pentagon's intelligence chief Stephen Cambone (search); Maj. Gen. Donald Ryder, the Army's provost marshal general; Maj. Gen. Geoffrey Miller, who commands U.S.-run prisons in Iraq; and Col. Thomas M. Pappas, commander of the 205th Military Intelligence Brigade implicated in the abuse of prisoners at Abu Ghraib prison.

The official spoke on the condition of anonymity, given the sensitive nature of the investigation.

A defense spokesman could not comment immediately Monday evening.

The panel of four former defense and congressional officials, selected by Rumsfeld, is in the midst of a 45-day review into the prisoner abuse scandal. Rumsfeld has said it is looking at "the pace, the breadth, the thoroughness of the existing investigations" and will determine whether more inquiries were needed.

But some have suggested the panel will not have enough resources or time, given its late July deadline, to conduct a thorough investigation.

In the statement, Schlesinger, a former defense secretary during the Nixon and Ford administrations, said the members are looking at current and past investigations, and began their own look into Defense Department detention operations.

"The American people should be confident that this panel will provide an unvarnished assessment of how these abuses happened and what needs to be changed in order for them to never happen again," Schlesinger said.

Monday's interviews were conducted in person and by secure videoconference at the Pentagon. Besides Schlesinger, who was defense secretary during the Nixon and Ford administrations, the panel includes former Defense Secretary Harold Brown, former Rep. Tillie K. Fowler, R-Fla., and retired Air Force Gen. Charles A. Horner, who designed the air campaign for the 1991 Gulf War.

All are members of Rumsfeld's Defense Policy Board.