WASHINGTON — Signs that Canadian citizens were involved in the attack by hostage-taking rebel militants on a remote gas plant in Algeria are of great concern to American authorities, US intelligence officials said on Thursday. While Algerian authorities apparently have not yet provided Western governments with cast-iron proof, a senior US intelligence official said, “We're taking very seriously the reports of the two Canadians' involvement.” Washington has also received intelligence indicating that Mokhtar Belmokhtar, the one-eyed militant who allegedly organized the gas plant attack, and other militants belonging to, or affiliated with Al-Qaeda's North African branch are plotting new attacks on Western interests, both in the region and beyond, US officials said. Confirmation that Canadian citizens were involved in the attack on the In Amenas facility in the Algerian desert would raise concerns about a worrying nexus between North America and North African militants. At least 38 plant workers, including citizens of Japan, the United States, Britain and France, and nearly 30 militants were killed in the operation to retake control of the facility. After their security forces stormed the facility, operated by Britain's BP and Norway's Statoil, Algerian officials said two Canadians were among the attackers and that one of them coordinated the attack. Some witnesses, whom Western national security sources consider credible, said one of the hostage-takers spoke English with either a North American or British accent. The US officials said they were concerned about growing indications that Westerners were traveling to join militant factions in hot spots like North Africa and Syria as part of a radicalization process that could motivate them to engage in violence on their return to their home countries. The officials acknowledged that those individuals could include citizens of countries whose passports qualify them to enter the United States without extensive background checks under a “visa waiver” program. Before the Algeria hostage-taking, many U.S. and allied intelligence experts regarded Al-Qaeda in the Islamic Maghreb, or AQIM, as a group involved mainly in criminal activities, including hostage-taking and drug trafficking, but whose political ambitions extended mainly to the immediate North African region where it operates.— Reuters