Thousands marched through Mexico City to demand that the government find out what happened to dozens of missing students who are feared to have been massacred by gang members and police in the state of Guerrero. The students from a teachers' college went missing after they clashed with police in the city of Iguala, in the volatile, gang-ridden state. Protesters carried photos of missing students and signs that read "Fascist government, assassin of teachers" as they marched from the financial district to a historic plaza. The Mexican government has sent federal forces to take over security in the city. Authorities said 28 bodies have been found at a mass grave site, and that some of the missing 43 students probably are among them.