Mexican protesters have fought running battles with police and set fire to the ruling party’s local offices in protest at the authorities’ handling of the case of 43 missing student teachers.
About 1,000 people marched in Guerrero state capital Chilpancingo, before unrest broke out, the BBC reported.
The disappearances have sparked a month of often violent street protests.
Local police, officials and drug gangs have all been implicated in the case, but no bodies have yet been found.
Municipal police officers had previously confessed to detaining the students and later handing them over to a local drug gang calling itself Guerreros Unidos (United Warriors).
Officials said last Friday that gang members had confessed to killing the 43 students and burning their remains near the town of Iguala, where they went missing on 26 September.
A group of forensic scientists, including teams from Argentina and the US, acting for the families said they had so far examined body parts from three locations uncovered during the investigations.
These included mass graves found in the hills around Iguala and the landfill site where the students are alleged to have been burnt.
In a statement the scientists said so far all the material they had been able to examine had not belonged to the missing students.
The disappearance of the 43 and the links it has revealed between the local authorities and the Guerreros Unidos have triggered mass protests.
Iguala residents say they suspect links between the gang and officials reach higher levels than that of the local town council.
