Mexico’s president said Tuesday a fight between gangs over drug and migrant trafficking routes was behind the massacre of 19 men in the southern state of Chiapas, according to AP News.

President Andrés Manuel López Obrador said the killings were part of a long-running dispute between two drug cartels.

“There are two groups that are in confrontation there, it’s been that way for a while,” López Obrador said. “What is the motive? The trafficking of drugs, and also the trafficking of migrants … there is a route there.”

He confirmed there were several Guatemalans among the victims, but he did not say whether they had been fighting for one side or another in the turf battles.

López Obrador said federal forces were “protecting the population” in Chiapas, despite the fact the area has seen several mass killings in recent months.

On Monday, authorities found 19 bodies piled in and around a dump truck in a cartel-dominated town near the border with Guatemala.

The men’s bodies were found in a truck abandoned on a rural road near the town of La Concordia, Chiapas. The bodies of fourteen men were piled in the bed of the dump truck, two more were found in the cab, two were just outside the truck and another body was found about 100 yards (meters) away.

The victims were shot to death, and included at least six men carrying Guatemalan identity documents.

The Public Safety Department said the killings appear to be related to the bloody turf battles between the Sinaloa drug cartel and a rival gang known as the Cartel of Mexico and Guatemala. The latter gang may have ties to Sinaloa’s arch rival, the Jalisco cartel.

As migrant smuggling and drug trafficking have become more lucrative in the area, the cartels have been fighting for control of smuggling routes over the last year.

The surge in violence in Chiapas state has led thousands of people to flee their homes.

In May, a mayoral candidate and five other people were killed when gunmen opened fire at a campaign rally in La Concordia, about 80 miles (125 km) from the border with Guatemala

A young girl was among the six people killed in the gunfire, along with mayoral candidate Lucero López Maza. Two others were injured, and the motive in the attack remains unclear.

That shooting came just days after 11 people were killed in mass shootings in a village in the township of Chicomuselo, Chiapas, a few dozen miles away from La Concordia.