WASHINGTON - Lawmakers leading the Senate investigation of the CIA's destruction of interrogation videotapes said there were gaps in yesterday's testimony by CIA Director Michael V. Hayden, and they outlined plans to call a series of witnesses as part of an expanding investigation.

"We had a useful and not-yet-complete hearing," Senate intelligence committee chairman Jay Rockefeller (D., W.Va.) said after the 90-minute, closed-door session with the CIA director. "There are a lot of questions to be answered."

Hayden said he sought to lay out a chronology of the agency's decision to begin taping interrogations of terrorism suspects in 2002 - during which agency officers employed a range of harsh methods - as well as the decision to destroy the recordings in 2005.

"I had a chance to lay out a narrative of the history of the videotapes, why the agency did it, why they were destroyed," Hayden said after the classified hearing. He stressed that he was not director when the tapes were made or destroyed.

"There are other people in the agency who know about this far better than I," Hayden said, "and I've permitted them to come on down and answer all the questions the committee might have."

Among those expected to testify in coming weeks are the CIA's acting general counsel, John Rizzo, and the former head of its operations branch, Jose Rodriguez, who authorized the tapes' destruction.

Rodriguez's decision is a focus of the Senate panel's investigation, as well as an internal investigation by the CIA and an inquiry by the Justice Department. Senate intelligence committee officials said the panel planned to issue a public report on its investigation after the Justice inquiry was finished.

Attorney General Michael B. Mukasey, addressing the CIA tape-destruction issue, resisted calls for an independent prosecutor.

"I think the Justice Department is capable of doing whatever it appears needs to be done" to determine whether the CIA broke any laws, Mukasey said yesterday during his first news conference as attorney general.

Asked about prospects for an independent counsel, he said the issue "isn't going to be faced until it has to be. And if it has to be, it will be."

Hayden's testimony yesterday focused on internal records that the CIA has gathered as part of its internal investigation.

The videotapes depicted CIA officials' use of harsh methods during the 2002 interrogations of al-Qaeda suspects Abu Zubaydah and Abd al-Rahim al-Nashiri.

Zubaydah, who is alleged to have had ties to the Sept. 11 plot, was subjected to waterboarding, in which a prisoner's face is covered with cloth and doused with water.

John Kiriakou, a former CIA officer involved in Zubaydah's capture, said in television interviews this week that Zubaydah had been uncooperative under questioning but relented after 35 seconds of exposure to the waterboarding technique.

Mukasey said yesterday that he still had not determined whether waterboarding is torture.

In a statement to the CIA workforce last week, Hayden said the agency destroyed the tapes only after it was determined that they were "no longer of intelligence value and not relevant to any internal, legislative or judicial inquiries."

The disclosure prompted questions of whether the agency had destroyed evidence illegally. New details have surfaced suggesting significant disagreements among top CIA officials over a two-year period before the destruction.

Former CIA officials said Porter J. Goss, the agency director in 2005, had opposed the tapes' destruction during meetings in which the issue was discussed. Senior agency lawyers also cautioned against doing so, although some had advised Rodriguez it might not violate any laws to destroy the tapes.

Rep. Rush D. Holt (D., N.J.) yesterday became the first lawmaker to request formally that Mukasey immediately appoint an independent counsel.

Neither the CIA's inspector general nor the Justice Department can fairly and independently investigate the matter, said Holt, a member of the House intelligence committee and chairman of its oversight subpanel.

Hayden is to appear today before the House intelligence committee.