Washington - A review of classified documents by former members of the Sept. 11 commission shows that the panel made repeated and detailed requests to the Central Intelligence Agency in 2003 and 2004 for documents and other information about the interrogation of operatives of Al Qaeda, and were told by a top C.I.A. official that the agency had "produced or made available for review" everything that had been requested.
A seven-page memorandum prepared by Philip D. Zelikow, the panel's former executive director, concluded that "further investigation is needed" to determine whether the C.I.A.'s withholding of the tapes from the commission violated federal law.
In interviews this week, the two chairmen of the commission, Lee H. Hamilton and Thomas H. Kean, said their reading of the report had convinced them that the agency had made a conscious decision to impede the Sept. 11 commission's inquiry.
Mr. Kean said the panel would provide the memorandum to the federal prosecutors and congressional investigators who are trying to determine whether the destruction of the tapes or withholding them from the courts and the commission was improper.
A C.I.A. spokesman said that the agency had been prepared to give the Sept. 11 commission the interrogation videotapes, but that commission staff members never specifically asked for interrogation videos.
The review by Mr. Zelikow does not assert that the commission specifically asked for videotapes, but it quotes from formal requests by the commission to the C.I.A. that sought "documents," "reports" and "information" related to the interrogations.
Mr. Kean, a Republican and a former governor of New Jersey, said of the agency's decision not to disclose the existence of the videotapes, "I don't know whether that's illegal or not, but it's certainly wrong." Mr. Hamilton, a former Democratic congressman from Indiana, said that the C.I.A. "clearly obstructed" the commission's investigation.