|Al Jazeera's Franc Contreras reports on the mass graves discovered just south of the border with the United States
Eleven mass graves have been found in the southern state of Coahuila, according to officials.
The Mexican army unearthed the graves in the village of Guerrero after an anonymous tip-off that led them to the area.
Friday's discovery comes as forensic experts continued to try and identify the remains of hundreds of people buried in mass graves in the north of the country.
The northern states are at the centre of a violent battle between rival drug gangs for control of lucrative smuggling routes to the United States.
Meanwhile on Friday, Mexican soldiers found a large buried cache of weapons apparently stockpiled by a drug cartel, including 154 rifles and shotguns and more than 92,000 rounds of ammunition.
The cache, found at a ranch near the industrial city of Monclova in the northern state of Coahuila, included four mortar shells, two rocket-propelled grenades, dozens of assault rifles, sniper rifles and two bows, the defence department said.
The seizure suggests that, despite efforts to crackdown on weapons trafficking in Mexico, drug cartels are still able to obtain enough weapons to keep stockpiles in reserve.
It was not the first such mass seizure in recent months. In May, soldiers seized 83 assault rifles and shotguns, five grenade launchers and more than 18,000 rounds of ammunition as well as hand grenades and 18 pistols following a confrontation with a 17-vehicle convoy of suspected cartel gunmen in the northern border state of Tamaulipas.
In December, soldiers in the northern state of Durango seized a cache of 84 rifles and 46 pistols.
In another development on Friday, Mexico filed charges against the alleged leader of a ruthless cell of the Zetas drug cartel who authorities say masterminded the mass killings of more than 250 people in a northern border state.
The federal Attorney General's Office says Martin Estrada Luna is charged with organised crime, kidnapping, drug trafficking and illegal possession of firearms.
Prosecutors said after Estrada Luna's April arrest that he was responsible for the slayings of 72 migrants last August and 183 people months later in Tamaulipas state, but he has not been charged with the killings.
The Zetas cartel has been fighting the Sinaloa cartel and other drug gangs for control of the border state.
The 34-year-old was born in Mexico and grew up in the US. He was deported to Mexico in 2009.
Source: Al Jazeera and agencies