27 February 2015
Last updated at 01:18
“They took them alive, we want them back alive,” read banners held at the march
The parents of 43 Mexican students who went missing five months ago have been leading a march in Mexico City to call for a full investigation.
Thousands of people have joined the protest, carrying banners with pictures of the missing trainee teachers.
Prosecutors say the students were arrested by corrupt police officers after a demonstration in the town of Iguala on 26 September.
They were handed over to a local criminal gang, who killed them.
The students attended a teacher training college in Ayotzinapa, in south-western Guerrero state.
The college has a history of left-wing activism but it is not clear whether the students were targeted for their political beliefs.
Forensic experts from the University of Innsbruck identified the remains of Alexander Mora
Jose Luis Abarca and his wife were arrested in November after weeks on the run
Attorney General Jesus Murillo Karam said the criminals burned the bodies in a nearby waste disposal site and scattered their ashes in a local stream.
Forensic experts in Austria carried out DNA tests on bone fragments found in a bag in the area and managed to identify one of the 43 students.
Analysis: Kate Watson, BBC News, Mexico City
It has been five months and the families still await answers but they are not giving up hope. The disappearance of the students has mobilised many Mexicans who say enough is enough.
One supporter at the march carried a sign saying she wanted to be one of the Mexicans to make a difference, not one of the many who seems indifferent to the thousands of disappearances in this country in the past few years.
The call for President Enrique Pena Nieto to step down can be heard loud and clear in the crowds here.
But relatives and independent investigators reject the official version of events.
They have held a series of demonstrations over the past five months to demand that the government do more to find the students.
Prosecutors believe the Iguala mayor, Jose Luis Abarca, ordered the students’ arrest because their protest disturbed a planned political speech by his wife, Maria de los Angeles Pineda.
Both have been arrested and charged with involvement with organised crime.