Mexico’s governing PRI party’s offices in south-western Guerrero state have been set on fire by protesters to vent their anger at the official handling of the case of 43 missing students.
Their disappearance more than six weeks ago from the town of Iguala has sparked a series of sometimes violent protests.
Officials say local gang members have confessed to killing the students and burning their bodies.
However, remains found nearby have not yet been matched to the missing.
About 1,000 people marched in the Guerrero state capital, Chilpancingo, before unrest broke out.
A group of protesters fought running battles with police, throwing stones and petrol bombs.
Officials said three police officers and two journalists were injured in the clashes.
The disappearance of the 43 trainee teachers and the links it has revealed between the local authorities and a gang calling itself Guerreros Unidos (United Warriors) have triggered mass protests.
Investigators said that municipal police officers confessed to seizing the students, who had been protesting in Iguala on September 26, and later handing them over to the gang.
Iguala Mayor Jose Luis Abarca is under arrest on suspicion of ordering police to intercept the students. Iguala’s police chief is still on the run.
Residents say they suspect links between the gang and officials reach higher levels than that of the local town council.
Relatives of the missing are also angry about the way the search for the students has been conducted.
The search uncovered a series of mass graves in the hills surrounding Iguala.
Tests carried out by the Guerrero state authorities suggested the bodies they contained were not those of the students.
Mexico’s Attorney-General Jesus Murillo Karam later said the initial tests may have been flawed.
A group of international forensic scientists acting for the families has also been examining the remains. On November 11 they released their first statement.
They said that they had so far been able to determine that 24 of the 30 bodies found in the six mass graves in Pueblo Viejo near Iguala were not those of the students.
It is not clear who they may belong to or how long ago they may have been buried there.
Test on the remaining six bodies found in Pueblo Viejo continue and results on those are expected soon, they said.
The team, made up of scientists from Argentina, Colombia, France, Mexico, Uruguay and the US, said it was also testing nine bodies found in burial pits in La Parota, also near Iguala.
Furthermore, charred remains found at a landfill site near the town of Cocula will be sent to a specialized laboratory in Austria for testing.
The landfill site is where, according to testimony by gang members given to prosecutors, the Guerreros Unidos killed and burned the students.
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