By David Ljunggren
OTTAWA (Reuters) - Two Canadians who took part in an attack by militants on an Algerian gas plant in January were in their early twenties and from middle-class backgrounds, the Canadian Broadcasting Corp. said on Tuesday.
Around 70 people died when Algerian troops stormed the Tigantourine desert gas plant and ended the siege. The Royal Canadian Mounted Police said last month they had identified two suspects but gave no details.
CBC named the two men as former high school friends Xristos Katsiroubas, 22, and Ali Medlej, who it said was about 24. Both came from London, a town in the central Canadian province of Ontario.
CBC cited police sources as saying Katsiroubas, who grew up in a middle-class home with a swimming pool and converted to Islam from the Greek Orthodox faith, was likely to be the attacker who survivors described as being blond-haired and speaking fluent "North American English".
The RCMP declined to comment. The Canadian Security Intelligence Service spy agency, which has repeatedly warned of the dangers of radicalized Canadians travelling abroad to cause trouble, did not respond to a request for comment.
A U.S. government source said U.S. agencies had received information about the Canadian investigation and believed that the CBC report correctly identified the Canadian militants who were killed in the Algerian hostage siege.
Canadian Foreign Minister John Baird said other nations such as the United States, Sweden and Britain were also struggling to deal with the same problem.
"Canada is far from the only country that has had to deal with this challenge of radicalization ... my colleagues and I will be discussing the issue in the days and weeks ahead," he said in a conference call from the United Arab Emirates.
Shortly after the gas plant attack, Algerian Prime Minister Abdelmalek Sellal said a Canadian gunman had coordinated the operation.
CBC said CSIS agents had interviewed family and friends of the two men in 2007. A former friend of the two said a relative had called the police, complaining the pair were "hanging around with weirdos".
CBC also said two other former schoolmates of the pair had travelled overseas with Katsiroubas and Medlej.
It cited intelligence sources as saying CSIS did not have the two men and their other friends under surveillance when they left Canada last year.
Christian Leuprecht, a terrorism expert, said the two men appeared to have become radicalized by themselves rather than having joined a militant cell in Canada.
"Much or all of the activity in which they would have been engaged while in Canada would likely have been perfectly legal. So these cases are difficult to detect, even harder to stop, and harder yet to convict," said Leuprecht, who works at Queen's University in Kingston, Ontario.
CSIS is aware of dozens of Canadians in their early twenties who have travelled or tried to travel overseas to take part in terrorism-related activities, the agency's director told a parliamentary committee in February.
A Canadian-Lebanese dual national was involved in the 2012 bombing of a tourist bus in Bulgaria that killed five Israeli tourists, Baird revealed earlier the same month.
U.S. intelligence officials say they are concerned by signs that Canadian citizens are involved in attacks abroad.
Canadian resident Ahmed Ressam, an Algerian citizen, tried to cross into the United States on a mission to blow up Los Angeles airport in 2000 and is serving 37 years in a U.S. prison.
(Additional reporting by Mark Hosenball; Editing by Paul Simao)