Intelligence increasingly shows al Qaeda is encouraging American and other western fighters in Syria to undertake special training to prepare them for possibly returning to their home countries to carry out attacks, US officials told CNN.National security officials are concerned that amid the mayhem of Syria's civil war, the global terror group has found a safe haven and a place where it again can recruit, plot and train operatives to carry out attacks on the US homeland, CNN reported.The official, who did not speak for full attribution, described scenarios in which foreign fighters arrive in Syria and are recruited by al-Qaeda to train for external attacks.The United States estimates up to 70 Americans have traveled to Syria, many with the purpose to join extremist groups.US homeland security and intelligence officials are trying to track them entering Syria and hope to do so, if they return to the United States.