MEXICO CITY – Soldiers and police found an outlaw camp in southern Mexico where a kidnap victim was rescued, human remains were found in a cooler and 12 bodies were extracted from clandestine burial pits.

The grisly find was made Tuesday in a part of southern Guerrero state where rival drug gangs have been engaged in a wave of extortion, kidnappings and turf battles.

Roberto Alvarez, the Guerrero state security spokesman, said a joint army-police patrol received a tip that people were being held at a rural encampment near a mountain in Zitlala, close to the violence-plagued town of Chilapa.

The patrol went to investigate, found the camp and freed a kidnapped man. They found no suspects, but did find gun magazines, vehicles and the cooler with human remains. Drug gangs frequently decapitate their victims and put their heads in coolers. Late Wednesday, Alvarez updated the number of bodies found in hidden graves to 12.

Army troops cordoned off the area and investigators were working to identify the bodies.

Survivors have testified in the past that criminal gangs in Guerrero sometimes operate rural camps where they hold, torture and kill kidnap victims.

And on Wednesday, state prosecutors said the body of another man was found buried in a clandestine grave near Guerrero’s Pacific coast.

Guerrero has seen an upsurge in gang-related violence. In recent days, dismembered or decapitated bodies have been found dumped on roadsides in different parts of the state.

In response, the government announced on Monday that it is stepping up the use of joint police-army patrols in areas known to be particularly violent.

The largely rural, impoverished state had 1,832 reported homicides in the first 10 months of 2016. If that rate continues unabated, Guerrero would be on track to have a homicide rate of about 60 per 100,000. That would rival the recent peak year of violence in the state, in 2012, when there were about 68 homicides per 100,000 inhabitants.