Mexican officials investigating videos shared on social media showing bodies in a dumper truck have found 19 corpses in La Concordia, in the southern state of Chiapas.

The victims were all male, dressed in black and wearing tactical vests, as worn by members of Mexico's powerful criminal gangs.

Most of the bodies lay inside the back of the truck, with three more found on a dirt track nearby. All had bullet wounds.

Crime cartels have been infiltrating the region, which is criss-crossed by transit routes used by migrants on their trek north to the United States.

The criminal groups extort money from the migrants and also use the routes to smuggle guns, ammunition and drugs from neighbouring Guatemala into Mexico.

Officials said they found Guatemalan identity papers on four of the bodies.

Members of the Chiapas prosecutors office had been alerted to a video uploaded to social media on 28 June.

In it, men identifying as members of the Sinaloa cartel show the bodies in the truck, claiming they are members of a rival gang that operates on the border between Guatemala and Mexico.

The next day, locals reported coming across the bodies near the community of La Concordia and reported their location to the authorities.

The Chiapas prosecutor's office said the victims were probably members of a group which they named as the "Chiapas and Guatemala cartel".

The gruesome find comes as a wave of gang-related violence has rocked La Concordia and its environs.

Last month, gunmen shot dead a woman who was running for mayor of La Concordia along with five other people.

Locals have described having to hide in their houses for days as gun battles rage in the streets as rival gangs fight for territory.

Hundreds have fled their homes.

The Mexican government says it has deployed members of the National Guard and the army to the area.

However, residents have in the past said that they feel abandoned and that the cartels return as soon as the federal forces leave.