FBI agents assisted CIA operatives and U.S. troops Wednesday in the interrogation of more than a dozen prisoners selected from among hundreds of captive Taliban and Al Qaeda fighters.

The prisoners were picked "because we concluded, in conjunction with people holding them, that these were people who might have important information and might be themselves senior people," Deputy Defense Secretary Paul Wolfowitz said.

Fifteen prisoners from the northern Afghan city of Mazar-e-Sharif were turned over Tuesday to U.S. Marines at a newly created jail at the American base in Kandahar, where FBI agents familiar with the Sept. 11 attacks arrived to help with questioning.

The prisoners arrived at Kandahar's airport at 10:30 p.m. local time — 1:00 p.m. EDT — just hours after the Marines officially opened their detention facility.

The first two captives were driven from the plane to the detention facility in a Humvee, apparently because they were unable to walk. The rest shuffled in from the tarmac bound at the hands and wrists, blindfolded and tied together in a line.

Officials believe they also may have key Al Qaeda figures among the five captives held in a Navy brig.

In addition to American John Walker and Australian David Hicks — both found among Taliban fighters — three other prisoners Wolfowitz described as "Taliban-slash-Al Qaeda" are being held on the USS Peleliu in the Arabian Sea.

"We think we know who they are, and if they're who we think they are, they're fairly important people," Wolfowitz said at a Pentagon news conference. "But one of the reasons not to start identifying them yet is we're not sure that their comrades necessarily know that we have them."

One prisoner is believed to be Abdul Aziz, a Saudi Arabian official of the Wafa humanitarian organization, said a U.S. official on condition of not being identified. Wafa's assets have been frozen by the Bush administration for alleged terrorist ties.

Hicks will also face questions from Australian officials. Attorney-General Daryl Williams said U.S. leaders are allowing the combined Australian Secret Intelligence Organization-Australian Federal Police team to question Hicks, who was captured in Afghanistan.

Thousands of prisoners were taken into custody by Afghan forces as they captured city after city in the two-month-old war. Americans have been questioning them and taking custody of those who might be of interest to the United States.

So far, however, captured fighters have given little reliable information on what U.S. officials want to know most — where to find Usama bin Laden.

"The task is still ahead of us," Secretary of Defense Donald H. Rumsfeld said during a news conference at NATO headquarters in Brussels, Belgium. "It's going to be tough, dirty, hard work."

Aside from prisoner information, U.S. officials have gathered documents and other items from caves in the Tora Bora region and buildings in Kandahar, the former Taliban stronghold.

Among things collected were some videotapes that have not been made public. Last week, the U.S. government released a tape featuring bin Laden laughing and boasting as he spoke of the destruction caused by the Sept. 11 terrorist attacks.

With the Taliban and Al Qaeda all but defeated and an interim Afghan government to be sworn in Saturday, the U.S. military says the war in Afghanistan has entered a new phase. No longer is success measured in territory taken; instead, it has transformed into a manhunt for bin Laden and his top deputies.

"It's going to be step by step, cave by cave, and to put a time limit on that would be imprudent right now," Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff, told reporters at the Pentagon.

Wolfowitz said any nation would be "crazy" to help shelter bin Laden.

"Any country in the world that would knowingly harbor bin Laden would be out of their minds," he said.

"I think they've seen what happened to the Taliban, and I think that's probably a pretty good lesson to people not to do that."

The Associated Press contributed to this report.