The hunt for the masterminds behind last month’s train bombings here has targeted an accused Al Qaeda operative who, although a fugitive wanted in connection with the Sept. 11, 2001, terrorist attacks in the United States, may have returned clandestinely to Spain to oversee the train plot, investigators said Tuesday. Witnesses told police they saw Amer Azizi, a Moroccan and longtime associate of several suspects in the train attacks, here after the March 11 bombings that killed 191 people, a senior investigator told The Times. Intercepted communications detected Azizi last year in Iran, where he was allegedly with Abu Musab Zarqawi, a Jordanian accused of leading an anti-U.S. bombing campaign in Iraq, Spanish investigators said.Full Story