Thirteen of the photographs appeared to be images already seen in the international media, but 11 have not been identified in previous investigations, according to a Pentagon letter to the Senate Armed Services Committee.

"They may not be original or true photographs," Powell Moore, assistant defense secretary for legislative affairs, wrote the committee.

He said they were given to the Criminal Investigation Command in Baghdad "under circumstances that warranted investigation, including forensic computer evaluation."

Moore said the committee would be told the results of the examination as they become available.

Two photos not previously seen in the media of U.S. soldiers posing with the body of a detainee at Iraq's Abu Ghraib prison were shown on U.S. television on Wednesday evening.

In separate photos shown on ABC News, Spc. Sabrina Harmon and Spc. Charles Graner are seen smiling and giving a "thumbs-up" sign over the body of a man identified by ABC as Manadel al-Jamadi, an Iraqi who died in U.S. custody at the prison.

ABC reported on its Web site that the photos were taken by Sgt. Charles Frederick, who in e-mails to his family questioned why those responsible for the prisoner's death were not being prosecuted in the same manner that he is.

Frederick, Harmon and Graner are among six U.S. military police facing charges over the abuse of detainees. A seventh soldier, Jeremy Sivits, was sent to jail and dismissed from the Army on Wednesday after pleading guilty in the first abuse trial.

Sen. John Warner, a Virginia Republican who chairs the committee, announced at a hearing on the abuses scandal at Abu Ghraib prison earlier in the day that the Pentagon had found another disc of images. But he said he had no other information at that time.