KANDAHAR, Afghanistan (CNN) -- The manhunt widened for terrorist mastermind Osama bin Laden in eastern Afghanistan and the Pakistani border on Wednesday as U.S. special forces continued operations in the Tora Bora region. 

U.S. B-52 bombers flew over the mountainous area, where bin Laden was believed to be hiding, but did not drop any bombs. During nighttime hours helicopters could be heard flying in the White Mountain region. U.S. special forces operating in the area refused to speak with reporters. 

Defense Secretary Donald Rumsfeld Wednesday said Pakistani forces have captured several hundred non-Afghan al Qaeda fighters who slipped out of Afghanistan and crossed the border. 

Speaking to reporters while returning from a NATO summit in Belgium, he gave few details, but said the fighters were from countries other than Afghanistan and Pakistan. Some of the prisoners showed signs of frostbite from the harsh winter conditions, he said. 

At a briefing at the Pentagon later on Wednesday, Rumsfeld said fleeing al Qaeda fighters were being "rounded up, contained and disarmed" by the Pakistani army, which he said was doing the "heavy lifting" in capturing any fighters attempting to flee to Pakistan. 

Of bin Laden, Rumsfeld said "we'll find him someday" but added that he was not the "entire problem." 

"The al Qaeda (are) the entire problem, and the other terrorist networks are the problem," he said. "So he is important, we're after him, we intend to find him, I believe we will, but we haven't. 

Rumsfeld said he was not prepared to say that al Qaeda was finished as a terrorist organization within Afghanistan. 

"They certainly aren't not functioning well," he said. 

U.S. military aircraft flew some 164 missions over Afghanistan on Tuesday without dropping any bombs, according to the Pentagon. 

Pentagon spokesman Dick McGraw said humanitarian supplies like blankets and dates were air-dropped in areas near Kandahar while propaganda leaflets were dropped around Tora Bora. 

Rumsfeld also said the detention center at the Marine-controlled Kandahar International Airport will be expanded to handle 500 prisoners 

CNN reported that Afghan commanders were pulling their troops out of the area, bringing with them prisoners captured during searches for bin Laden in the region's cave complexes. 

Caves stocked with weapons
On Wednesday, CNN Correspondent Amanda Kibel viewed caves in mountains 10 kilometers (6.2 miles) north of Kandahar along with a house reportedly used by bin Laden. They were stockpiled with hundreds and thousands of weapons and munitions left behind by al Qaeda fighters who fled Kandahar. 

The house is a three-room stone structure that bin Laden used when "he felt threatened," and he fled from the house after the U.S. bombings began, Kibel reported. 

Kibel said the CNN crew was taken to the series of underground bunkers by a former mujahedeen commander. Afghan ground forces were led to the area by former Taliban fighters. 

There were signs the fighters left in a hurry with religious materials, clothes and weapons left behind. The caves were piled high to the ceiling with weapons and munitions. About 1,000 weapons and munitions were stockpiled in bin Laden's house. 

Afghan officials said the great number of weapons seemed to indicate that bin Laden and his al Qaeda fighters were getting ready for a battle. 

The anti-Taliban fighters have begun clearing the caves. Any weapons they find will be taken to Kandahar, delivered to the government and are eventually intended to be used by the Afghan army. 

The caves were far more rudimentary than the sophisticated Tora Bora caves, the officials said. The caves north of Kandahar were structures dug into mountains for small groups of people in live in. 

Not far from the caves, three or four bomb craters were seen. CNN was told that bomb craters were underground living areas of al Qaeda fighters. 

13 killed in prisoner revolt
In Pakistan, 13 people -- including seven al Qaeda prisoners -- were killed when prisoners took over a bus near the Pakistan-Afghanistan border Wednesday, according to local commanders in Pakistan. 

The local commanders said seven al Qaeda prisoners and six Pakistani security people were killed. Another 21 al Qaeda fighters escaped. 

A convoy buses was transporting from Parachinar to a detention facility in Kohat. En route, there was a tussle on one of the buses. 

The prisoners grabbed guns and opened fire. During the incident, the bus overturned and went into 20-foot ravine. 

Twenty prisoners were apprehended, but 21 others got away and were being sought by local authorities. 

More than 155 prisoners had been arrested crossing the border from Afghanistan's Tora Bora region into Pakistan. 

Fifteen captured al Qaeda and Taliban fighters are in custody Wednesday at the newly built detention facility at Kandahar's airport, and the FBI says it is ready to begin questioning them. 

The prisoners arrived late Tuesday at the facility after being brought from a prison near Mazar-e Sharif in northern Afghanistan and were to be questioned soon by FBI agents. 

The prisoners -- the first to be brought to the detention facility at the Kandahar airport -- were captured in fighting around Tora Bora. 

They were searched, screened, blindfolded, gagged, bound at the hands and wrists, and chained together in a line when they were brought from the plane to the facility. 

Eight FBI agents are at the airport to interview the prisoners. FBI Special Agent Tom Knowles, who is at the airport, said the agents will be trying to learn about planned future al Qaeda attacks and want to collect information about past actions, including the attacks on the World Trade Center and Pentagon on September 11. 

The Marines said the men will be safeguarded and provided with medical care and food, shelter and water. They will be held pending further disposition, but allowed to practice their religion and to meet with the International Committee of the Red Cross, according to the Marines.

U.S. Deputy Defense Secretary Paul Wolfowitz said Tuesday that the 15 prisoners were "selected because we concluded ... that these were people who might have important information or might themselves be senior people." 

An additional five detainees, including U.S. citizen John Walker, remain held aboard the USS Peleliu in the Arabian Sea. 

Peacekeeping force taking shape
A British-led multinational peacekeeping force planned for Afghanistan will not be operational until mid-January, UK defense officials said. 

British Defense Secretary Geoff Hoon told parliament on Wednesday that Britain would contribute 1,500 to the force, which would have a total strength of between 3,000 and 5,000. 

Britain would lead the force for around three months, before handing over control to one of its partners, Hoon said. 

In Rome, incoming Afghan transitional government leader Hamid Karzai, said he felt the "weight of responsibility" with his new role but added his country would see that "the fight against terrorism is taken to its end, its absolute end." 

He said he would tackle terrorism, "warlordism" and the rule of the gun in a country that will need rebuilding almost from scratch. Karzai met with former Afghan King Mohammed Zahir Shah in Rome to discuss the king's return to Afghanistan. The ex-monarch was deposed in 1973. 

Elsewhere, Yemeni security forces Wednesday were fighting their way into the hideouts of several suspected members of bin Laden's al Qaeda network, diplomatic sources in Yemen told CNN. 

The suspects now being hunted had probably been in the southern Arabian nation for some time, the sources told CNN. The sources said the suspects were more likely to be wanted by the United States in connection with the October 2000 attack on the USS Cole when it docked in Yemen than to be anyone who had recently fled from Afghanistan.