Anti-riot police have been deployed to the Mexican city of Chilpancingo after protesters attacked local government buildings in anger at the disappearance of 43 students on 26 September.
Hundreds of demonstrators set fire to part of the Guerrero state headquarters and demanded the resignation of Governor Angel Aguirre.
The protesters say the authorities are not doing enough to find the students.
They disappeared after clashing with police in the town of Iguala.
The protesters allege that the police rounded up the missing students before handing them over to a local drug gang called Guerreros Unidos.
The students all attended a local teacher training college with a history of left-wing activism but it is not clear whether they were targeted for their political beliefs.
They disappeared after deadly clashes with the police in which six people died. Eyewitnesses reported seeing them being bundled into police vans.
Prosecutors have detained 26 police officers in connection with the clashes on 26 September, as well as four gang members and four other unidentified people.
Relatives and friends of the missing have become increasingly angry at the perceived slow pace of the investigation.
DNA tests are still being carried out on remains found in several mass graves discovered outside Iguala, some 200km (125 miles) south of Mexico City.
Governor Aguirre said on Saturday that the students were not among the bodies identified so far, but did not clarify how many of the badly burnt bodies had been tested.
Thousands of people have taken to the streets across Mexico to demand government action to locate the missing students.
On Monday, demonstrators gathered outside the government complex in Chilpancingo, allowing workers to leave before ransacking and setting fire to the building and a vehicle parked outside.
They vowed to "radicalise" their actions if there was no progress in the investigation.
President Enrique Pena Nieto went on national television at the weekend to promise to identify and punish those responsible for the disappearances.
He described the incident as "shocking, painful and unacceptable" and said there would be "no impunity".