Federal agents escort policemen detained in connection with the disappearance of the students of Ayotzinapa Teacher Training College "Raul Isidro Burgos", at the Attorney General's Office premises in Mexico City October 17, 2014. The students went missing in the southwestern state of Guerrero on September 26 after clashing with police and masked men, with dozens of police being arrested in connection with a case that has sent shockwaves across Mexico. Authorities say many of the missing students were abducted by police. REUTERS/Tomas Bravo (MEXICO - Tags: CIVIL UNREST CRIME LAW POLITICS)