A mortar shell fell in central Baghdad's Green Zone early Monday, just hours before Saddam Hussein's trial was set to begin, but there were no report of injuries, police said. The shell was fired from the Dora neighborhood in southern Baghdad, said police Lt. Bilal Ali Majeed. A roadside bomb also detonated next to a passing US Army convoy in northeastern Baghdad Monday, setting fire to a Bradley fighting vehicle. Police Capt. Mohammed Abdul-Ghani said three soldiers were injured, but no other information was immediately available. In Canada on Sunday, a Parliament official said four aid workers, including two Canadians, had been kidnapped in Iraq but refused to name their group or say where they were seized.