Mexican protesters burn state congressional building as search for missing students continues
Firefighters try to extinguish the fire on vehicles set ablaze by protesters in Chilpancingo, Guerrero State, Mexico on Nov. 12, 2014. Photo by Pedro Pardo for Agence France-Presse.

Protesters fuming over the disappearance of 43 college students set fire to a state congress in southern Mexico on Wednesday in another day of angry demonstrations over the presumed massacre.

Some 500 masked students and radical teachers broke into the empty Guerrero state legislature and burned the library and the chamber where local lawmakers hold sessions.

Moments earlier, protesters torched the education department's audit office in another part of the state capital Chilpancingo.

Violent protests have erupted in Mexico since authorities said Friday that gang hitmen confessed to murdering the students and incinerating their bodies after corrupt police handed over the 43 young men in September in Guerrero.

The case has turned into the biggest crisis of President Enrique Peña Nieto's administration, undermining his assurances that his security strategy to combat years of drug violence was finally bearing fruit.

Peña Nieto traveled to China for summits this week, brushing aside critics who said he should have stayed home to deal with the crisis.

Protesters set fire to the Guerrero state headquarters of his ruling Institutional Revolutionary Party (PRI) in Chilpancingo on Tuesday, one day after blocking access to Acapulco's airport for several hours.

The state's governor, Angel Aguirre, resigned last month after protesters burned part of the government palace over his handling of the mass disappearance. He was replaced by an academic, Rogelio Ortega.

- DNA tests pending -

The students vanished on September 26 after police shot at their buses in the city of Iguala, killing six people, and delivered the 43 to the Guerreros Unidos drug gang, authorities say.

The young men, who are from a teacher college known for its radical leftwing activism, had traveled to Iguala to collect funds but also stole four buses to return home when they came under fire.

Prosecutors say the city's mayor ordered police to confront the students over fears they would disrupt a speech by his wife.

Last week, Attorney General Jesus Murillo Karam said gang suspects told investigators that they killed the students in a landfill, burned their remains in a 14-hour bonfire, crushed them, and dumped them in a river.

But he stopped short of declaring the young aspiring teachers dead, saying DNA tests on remains were pending.

- 'Redouble' search effort -

Interior Minister Miguel Angel Osorio Chong told parents of the missing during a meeting Tuesday that authorities will "redouble" search efforts and that the investigation remains open.

At the request of the families, the government signed an agreement with the Inter-American Commission on Human Rights on Wednesday to provide technical assistance in the investigation.

The regional rights body can suggest "criminal complaints or contest decisions" taken by the government during the investigation, said deputy foreign minister Juan Manuel Gomez Robledo.

Parents of the students, who deeply distrust the government, refuse to believe they are dead and say they will only believe DNA results from independent Argentine forensic experts.

Charred remains found in the landfill and river in the town of Cocula, near Iguala, will be sent Wednesday to forensic specialists at Austria's University of Innsbruck.

The university's medical institute has used its expertise in several high-profile cases, including identifying some victims of the 2004 South Asian tsunami.

The institute worked with U.S. experts to identify the remains of the son and daughter of Russia's last tsar in 2008.

That same year, the lab was able to identify 13 victims of Augusto Pinochet's dictatorship in Chile after analyzing 47 bones.