Soldiers in Mexico have uncovered a mass grave with at least 18 bodies in the northern state of Nuevo Leon. Investigators believe drug gangs used the remote spot to torture and execute their victims. In the past weeks, two more such graves have been discovered in Nuevo Leon, which is at the centre of a violent battle between rival drug gangs. The bodies were found in a pit, east of the city of Monterrey, measuring 70m by 40m. Nuevo Leon has seen an increase in violence which police say stems from a deadly fight between the Gulf cartel and their former gang of hit-men, the Zetas, for control over the lucrative drug routes to the United States.