Protesters attacked Mexico's Attorney General headquarters in the country's capital Wednesday demanding answers after 43 students went missing last month in the violent southern state of Guerrero.

Frustrations were amplified Tuesday after officials confirmed none of the 28 corpses found in a Guerrero mass grave belonged to the missing students.

Violence in Guerrero, the home state of Acapulco, is becoming a major issue for President Enrique Pena Nieto, who took office two years ago pledging to end a wave of violence that has killed about 100,000 people since the start of 2007.