Two Muslim men authorities say played a key role in a 2009 al Qaeda plot to bomb packed New York subway cars now face charges in Canada, although their whereabouts are unknown

Canadian police have accused Ferid Imam, a former student at the University of Manitoba, of training Najibullah Zazi, the Afghanistan-born New Yorker who has pleaded guilty to trying to bomb the city's subway system. Imam was identified by the New York plotters as a weapons instructor who went by the name of "Youseff," police said. Imam, 30, is charged with instructing to carry out terrorist activity and conspiracy to participate in the activity of a terrorist group. Another Muslim, Maiwand Yar, 27, was charged with conspiracy to participate in activity of a terrorist group and participation in the activity of terrorism. Yar is also a former student at the University of Manitoba. Imam and Yar are now the subjects of an international manhunt that is believed to include the CIA. Canadian authorities said the Muslims left their homes in Manitoba in 2007, bound for Pakistan, in order to train for and carry out terrorist acts against NATO forces in Afghanistan. Police believe the suspects were in the tribal areas of Pakistan about a year ago, but have had no credible intelligence about their whereabouts since then. Canadian counterterrorism and government officials say the radicalization of these men, and others from North America and Europe represents a true reflection of a dedicated group of Islamic recruits that pose a direct threat to national security. U.S. authorities charged Imam in July 2010 with providing material support and receiving military-type training from al Qaeda. Federal prosecutors allege that Imam, while in Pakistan in 2008, helped train Zazi and Zarein Ahmedzay to detonate bombs on subway trains on the eighth anniversary of the September 11 attacks. Imam is also charged with use of a destructive device.