KABUL — An investigation into the October mine blast that killed two Canadian soldiers in Afghanistan has not been able to establish conclusively that terrorists were behind the strike, the commander of the NATO-led force in Kabul said Wednesday.

"The formal overall inquiry will not have found, unfortunately, a final end," said Lt.-Gen. Goetz Gliemeroth of Germany.

However, Gliemeroth, head of the International Security Assistance Force, said despite the inconclusive finding he is personally convinced the two soldiers died as the result of an act of terror.

And Gliemeroth told a news conference at ISAF headquarters that he believes a man now being held by U.S. authorities in Afghanistan was responsible for the attack.

Abu Bakr was arrested Oct. 7 by Kabul police, with the help of Canadian, British and German forces. Bakr was the Kabul-area commander of Hezb-e-Islami Gulbuddin, or HIG, described by the Canadian contingent's top soldier as the third-largest terrorist organization in Afghanistan after al-Qaida and the Taliban.

"There is very strong evidence that that very man had been involved (in the blast)," said Gliemeroth.

Sgt. Robert Short and Cpl. Robbie Beerenfenger died Oct. 2 when at least one anti-tank mine hidden on a sandy track in hills south of Kabul exploded under their vehicle during a routine patrol. Three other soldiers were injured.

Several top HIG agents have been arrested in Kabul and "more than a total of three main actors" in the organization run by warlord Gulbuddin Hekmatyar have been detained, Gliemeroth said.

He didn't identify the other men or provide further details, including when the other arrests were made. He said the investigation was continuing.

Hekmatyar is a former Afghan prime minister and now an ally of the ousted Taliban regime which has recently stepped up attacks inside Afghanistan.

Gliemeroth said Kabul police sent the men for detention to the main U.S. military base at Bagram, north of the capital.

U.S. military spokesman Lt.-Col. Bryan Hilferty said he couldn't comment on any detainees at Bagram, where the American military has a jail for terrorist suspects.

Gliemeroth commands the 6,100-member force that patrols the Afghan capital and recently added a base in the northern city of Kunduz. There are 2,000 Canadians stationed in or around Kabul as part of ISAF.

Kabul has been largely spared the attacks that have plagued U.S. and Afghan troops, government targets and aid workers in the south and east, where about 60 people have been killed this month alone. Most of those killed have been civilians.

However, Gliemeroth said the capital remains at risk. Last June, four German peacekeepers were killed in a suicide attack on their bus. In November, a bomb shattered windows at one of Kabul's few up-market hotels. And last month, a bomb destroyed a wall outside a UN guest house in the capital.

Those attacks have been carried out "very professionally," he said, saying the attackers could still be in Kabul.

In Kunduz, German forces have taken over a so-called Provincial Reconstruction Team, a joint security-reconstruction operation established by the United States.

Gliemeroth said ISAF will probably have taken over another five PRTs in the Afghan provinces by the end of the year, mainly in the largely stable north and west.

Britain, New Zealand and the United States already run teams in those regions _ a move to improve security and encourage Afghan authorities and aid workers to help in reconstruction. Italy, Norway and Sweden are also expected to provide troops who can operate in the provinces under ISAF command.

Canada has been considering whether to provide its own PRT in Afghanistan, however no decisions are expected from Ottawa until late next month at the earliest.

Gliemeroth said countries must also deploy extra equipment and a special rapid-reaction force in case they need to extract soldiers and civilians from far-flung areas in an emergency.

That widening of the peacekeeping mission is supposed to free up U.S. forces which are establishing new security teams across the troubled south and east in time for summer elections.

The United Nations, which has long pushed for the peacekeeping operation to be expanded nationwide, has warned that the vote can only go ahead if security improves.

Gliemeroth said he expected other countries to announce extra support for the security mission in February.