Mock coffins, representing the fatal victims of the September 26 shooting against students from the Ayotzinapa Teacher Training College and members of a football team, are placed outside Palacio Nacional in downtown Mexico City November 1, 2014. The students disappeared in Iguala on September 26 after they clashed with police and masked men. Security forces have combed the area around Iguala in search of the students, whose disappearance has sparked massive protest marches in Mexico and which has become arguably the sternest challenge yet to face Mexico's President Enrique Pena Nieto. REUTERS/Tomas Bravo (MEXICO - Tags: CIVIL UNREST CRIME LAW POLITICS)