The Islamist militants who attacked an Algerian natural gas plant in the Sahara last week were well-organized, had insider information and their numbers included two Canadians, the country’s prime minister said Monday.

Abdelmalek Sellal claims that two Canadians were among the terrorists who attacked the plant Wednesday, taking hundreds hostage before a bloody siege ended the crisis over the weekend.

Ottawa has not been able to confirm reports that Canadians were involved in the four-day siege. Foreign Affairs Minister John Baird said Monday his department is investigating.

"We can't confirm the accuracy of these reports. But what we are doing, our embassy in Algiers and our team in Ottawa are working to try to verify these informations and get the names of these alleged Canadians. But we can't report anything official at this time," Baird told CTV News Channel.

The Algerian prime minister would not say whether the purported Canadians were killed when Algerian troops stormed the plant, or were among the three militants who were captured alive.

Speaking at a news conference Monday, Sellal said the militants came from Egypt, Canada, Mali, Niger, Mauritania and Tunisia, adding that Algerian forces killed 29 of the 32 militants when they stormed the facility.

According to the latest tally, 38 hostages were killed, including seven Japanese and three energy workers from the U.S. and three from the U.K. Five foreign workers are still unaccounted for.

The Algerian interior ministry had said earlier that forces were able to free "685 Algerian employees and 107 foreigners" after they stormed the plant. One permanent resident of Canada who was at the site is safe, and has reportedly departed Algeria.

Sellal's account on Monday was the first official Algerian narrative of what happened during four days of terror at the plant, located roughly 1,200 kilometres from Algiers.

The standoff began Wednesday, and by the time Algerian troops stormed the facility on Saturday, dozens of people had been killed, though many of the bodies were so badly disfigured it was unclear how many of them belonged to hostages or militants.

Sellal said Monday only one of the attackers was Algerian -- a man who served as a driver for the group. The rest of the attackers were foreigners, including a man from Niger who used to work at the plant and "knew the facility's layout by heart."

During the standoff, the militants had boasted that their group included members from Canada, said Paul Schemm, a reporter with The Associated Press based in Morocco.

One terrorism experts says no one should be surprised to hear of a Canadian citizen’s involvement in terrorist activities abroad.

“Canadian involvement in overseas terrorism has been growing,” John Thompson of the Toronto-based Mackenzie Institute told CTV’s Power Play.

When Foreign Affairs Canada hears about a Canadian getting killed in a terrorist attack, “they need to find out if he’s a victim or one of the perpetrators,” Thompson said.

Samantha Nutt, author and founder of War Child North America, said while it’s “conceivable” that a Canadian could have joined a terrorist network in North Africa, it’s still too early to tell if reports from Algeria are correct.

“We need to do due diligence here and try to see where the evidence takes us,” she told Power Play.

The Algerian siege began when militants attempted to hijack two buses at the gas plant. The attackers were initially driven back, but then managed to seize the sprawling facility.

On Monday, security experts were still working to defuse mines planted throughout the facility. It's believed the militants planned to destroy the plant and kill all the workers.

A militant Islamist group known as the Masked Brigade claimed responsibility for the attack, saying it was retribution for the French-led military intervention in Mali, designed to stop Islamist militants from establishing a foothold in the country's north.

The group warned there could be many more attacks of a similar nature.

"We stress to our Muslim brothers the necessity to stay away from all the Western companies and complexes for their own safety, and especially the French ones," said a statement from the group.

The group is led by Moktar Belmoktar, the one-eyed Algerian founder of the group. The group, which was originally formed in Algeria before being driven into the Saharan region near the borders of Mauritania, Mali and Niger, has claimed in the past to have Canadians among its membership.

Schemm said the attack at the natural gas plant represents a significant escalation in violence by a terror group in the region.

"This is easily the most audacious attack that has happened in North Africa by a militant organization like this," he said.