A Saskatchewan-born soldier was fatally shot during a firefight in Afghanistan early Saturday, and the military is investigating whether he was killed by friendly fire from civilian security personnel.

Master Cpl. Josh Roberts belonged to 2nd Battalion, the Princess Patricia's Canadian Light Infantry based in Shilo, Man. His fianc�e was expecting a child.

The soldier was involved in a joint operation designed to disrupt Taliban activity in the volatile Zhari district, a farming area west of Kandahar City. Canadian soldiers engaged a group of about 15 insurgents as a private security company's convoy passed through the area.

The military is investigating whether personnel in the convoy accidentally fired on the Canadian soldiers.

"Until we have conclusive results of the investigation, I can't give you a definitive statement," Brig.-Gen. Dennis Thompson, commander of Task Force Afghanistan, told reporters during a briefing at Kandahar Airfield.

Soldiers with Charlie Company administered first aid to Roberts at the scene. He was then taken by armoured vehicle to the closest combat outpost and transferred by helicopter to the Role 3 multinational hospital at the airfield base, where doctors pronounced him dead.

Maj. Bob Ritchie, taskforce commander for Zhari District, said it's not rare for private security contractors to fight with insurgents in the notoriously violent region.

"Private contractors routinely operate within the battle space and they provide essential security to a lot of development and stabilization groups," he told The Canadian Press. "I don't know whether they had a legitimate target or not. There's going to be an investigation into all of this activity."

Thompson said that if it weren't for the security services provided by private firms, "it would be impossible to achieve what we're achieving here."

But Prof. Nasir Islam, an expert on Afghanistan at the University of Ottawa, said some security firms had developed a reputation for being overly aggressive.

"Supposedly they are efficient at what they do, but they are also pretty trigger-happy," he told CTV News.

Roberts transferred to the regular Forces from the North Saskatchewan Regiment in 2006. His superiors promoted him to master corporal only two weeks ago.

"His best friend describes him as a no-nonsense kind of guy who lived like people dreamed; he was a fun-loving and genuine individual who was totally dedicated to the Army and held his section together. He looked out for his guys in ways they probably didn't realize," Thompson said.

"We are deeply affected by this loss. Josh will be greatly missed by his military family."

Prime Minister Stephen Harper issued a statement Saturday calling Roberts a "great Canadian" who will "not be forgotten."

Canada has lost 89 military personnel in Afghanistan since 2002. A Canadian diplomat has also been killed.

With a report by CTV's Rosemary Thompson and files from The Canadian Press