DNA collected in Bin Laden hunt

Canadian troops spearheaded the mission

Troops from the US-led coalition in Afghanistan have been gathering human DNA samples in the mountains of Tora Bora to see if Osama Bin Laden died there.

Al-Qaeda terror group leader Bin Laden - accused of masterminding the 11 September attacks on the United States - was believed to have fled the eastern region during heavy fighting late last year.

Bin Laden: Fled... or dead?

However, there is also speculation he might have been killed by US air strikes along with his ally, Taleban leader Mullah Mohammed Omar.

Four hundred Canadian troops and a small number of American military investigators spent three days searching the area's cave complexes, tunnels and bunkers.

The samples they took from bodies of al-Qaeda and Taleban fighters will be analysed and the DNA results compared with a list of the most wanted al-Qaeda and Taleban leaders - a list topped by Bin Laden and Mullah Omar.

Bin Laden's bodyguards?

At least one cave complex which had been sealed by bombing in December's battle had to be reopened by the troops so they could carry out their searching and testing.

DNA samples were also taken from 23 bodies unearthed from a village cemetery that the Canadians believe may contain the bodies of Bin Laden's bodyguards.

Mullah Omar: Spiritual leader of the Taleban

One prominently marked grave was initially thought to be that of Bin Laden himself, but visual inspection of the body within apparently showed that was not the case.

The bodies were reburied after the inspections.

During their mission, the Canadian forces also found what they described as substantial information to help the planning of future missions in Afghanistan.

Before they left, the coalition forces destroyed numerous bunkers, firing positions and cave systems, including what they describe as one major cave complex.

The Americans say that hundreds of al-Qaeda members were killed in the fighting at Tora Bora late last year, but the figures are disputed.

It is believed that many of the fighters who were there escaped, possibly over the border into Pakistan.

US military criticised

The Pentagon had previously asked Bin Laden's relatives to provide DNA samples to help determine if human remains found in Afghanistan were those of the terror group leader. It is unclear if they complied with this request.

The US-led coalition has been stepping up its search for al-Qaeda and Taleban fighters in recent weeks, exploring caves and bunkers they were suspected of having used in the recent past.

The BBC's David Chazan says that however much American leaders try to downplay his importance, some Americans still equate success in Afghanistan with getting rid of Bin Laden.

He adds that the renewed focus on his fate comes a few weeks after American military commanders were criticised for allegedly letting him slip away from Tora Bora.