Latest march sees thousands demand return of 43 students who went missing last month after being attacked by police

Pressure continues to mount on the Mexican authorities to find 43 student teachers who disappeared three weeks ago in the southern city of Iguala, many of them after being arrested by local police.

Thousands marched through the resort city of Acapulco on Friday calling for the return of the students alive in the latest in a series of protests around the state of Guerrero, where the events happened, as well as in other parts of the country and abroad.

At the same time police on horses with sniffer dogs are searching the hills around Iguala for signs of the students.

Since the students went missing on 26 September, after being attacked by municipal police and unidentified gunmen, at least 19 mass graves have been discovered in these hills.

Federal attorney general Jesús Murillo said on Tuesday that none of the 28 bodies found in the first five graves belonged to the missing students. No information has yet been made public about the bodies found in any of the others.

Friday’s march in Acapulco took place under stormy skies, filling the boulevard that rings the resort’s famous bay. It was headed by relatives of the disappeared, as well as a sizable contingent of other students from Ayotzinapa, the name of their famously radical teacher training college that is also in Guerrero.

With tension running high prior to the protest, the US embassy issued a warning to tourists to stay away from the march. The city’s authorities suspended classes at local schools, urged businesses to shut up shop, and citizens to stay at home.

The march, however, was notably peaceful with no sign of the kind of violence that has accompanied some previous demonstrations. On Monday protestors burned out government buildings in the city of Chilpancingo, the state capital.

Apparently worried that such events could reduce solidarity for their cause, some 300 students from the college spent Thursday sweeping and removing rubbish from the streets in Chilpancingo. One of the organisers told local newspaper El Sur that they wanted to show thanks to residents of the city for their support.

The case of the disappeared students has become a powerful symbol of the broader failure of municipal, state and federal authorities to contain the influence of organised crime in Guerrero, with striking parallels evident in several other parts of the country.

A local drug cartel that calls itself Guerreros Unidos had allegedly infiltrated the municipal government of Iguala from the mayor down. Mayor José Luis Abarca is now on the run.

This week the investigative TV news programme Punto de Partida broadcast testimonies of relatives of people disappeared at checkpoints at the entrance to Iguala. The check points were reportedly set up by the police and the cartel together in order to prevent rival gangs from entering the city.

Alejandro Ramos, of a local human rights group, told the programme that relatives of people disappeared in Iguala are beginning to tentatively come forward in the hope that their loved ones will now also be included in the search for the students.