A C-130 leaves Camp Rhino. The plane is the biggest aircraft currently able to land at Kandahar airport

TORA BORA, Afghanistan  -- Afghan fighters were conducting cave-by-cave searches Tuesday, looking for al Qaeda fighters and Osama bin Laden, as 15 of bin Laden's soldiers arrived in Kandahar for questioning by FBI agents.  Meanwhile, many of the al Qaeda fighters in Tora Bora who had been fighting with local tribal troops are believed to have fled toward Pakistan.  In Washington, Marine Gen. Peter Pace, vice chairman of the Joint Chiefs of Staff, said there were no bombing missions Tuesday, but added that U.S. aircraft continued flying over the country and were available for airstrikes.  Pace said searching the caves would take time, as there are hundreds of caves in the Tora Bora area.  "It's going to be step by step, cave-by-cave, and to put a time limit on that would be imprudent," he said.

U.S. Deputy Defense Secretary Paul Wolfowitz reiterated that the United States does not where bin Laden is, saying most of the reports on bin Laden's location are based on "second-hand" information. 

Bin Laden has few options if he were to escape Afghanistan, Wolfowitz said. 

"Any country in the world that would knowingly harbor bin Laden would be out of their minds," he said. "I think they have seen what happened to the Taliban and I think that is probably a pretty good lesson to people not to do that." 

Prisoner interviews
Escorted by U.S. Marines, the captured al Qaeda fighters arrived late Tuesday at the newly built detention center at Kandahar International Airport, where they are to be questioned by eight FBI agents. 

Wolfowitz said that 15 prisoners were "selected because we concluded ... that these were people who might have important information or might themselves be senior people." 

The fighters were transported to Kandahar from a prison near Mazar-e Sharif in northern Afghanistan. They are the first prisoners to be brought to the Kandahar facility. 

Authorities released few details about the captives, refusing to give out their names or say if any top al Qaeda leaders were among the group. 

Two of the prisoners were driven to the entrance of the detention center, apparently because they were injured and had trouble walking. The rest were led in about 20 minutes later, shuffling in a line, their hands and feet bound. 

FBI agents want to learn about any planned future attacks, plus intend to glean information about past actions, including the September 11 attacks in New York and Washington, and the bombings of the U.S. embassies in Kenya and Tanzania in 1998. 

Marines said the men would be safeguarded and provided with medical care, food, shelter and water. 

The prison from where the men came is the same building where Taliban and al Qaeda fighters staged a bloody prison uprising late last month that claimed the life of a CIA agent. It was not immediately known if those in custody participated in that uprising. 

The intelligence chief of Kandahar province, Haji Gulalai, said there are indications supreme Taliban leader Mullah Mohammed Omar is believed to be in Helmand province, west of Kandahar, in a district called Baghran. 

Wolfowitz said Omar is "probably" in the Kandahar area. 

In addition, sources told CNN that Yemeni forces initiated an attack Tuesday in an area of the country where authorities believe a member of al Qaeda is hiding.

Celebrations, not missiles
At Kandahar, two U.S. military C-130 transport planes originally believed to have come under fire from surface-to-air missiles in separate incidents were not attacked, U.S. officials said Tuesday. 

Originally, Marines here said muzzle flashes were believed to be missiles, but further analysis showed that was incorrect, officials said. Those flashes apparently were part of the Eid al-Fitr celebrations marking the end of the Muslim fasting month of Ramadan, said Maj. Ralph Mills of the U.S. Central Command in Florida. 

"There were no missile explosions," he said. 

Neither plane was damaged and the crew members are safe, Mills said.