REYNOSA, Tamaulipas – Mexican authorities found the remnants of a fierce gun battle between rival cartels immediately south of the Texas border. The fighting left 21 dead and five torched vehicles.

The shootout is believed to have been started when a team of gunmen from the Northeast Cartel faction of Los Zetas made an incursion into the town of Refugio Hinojosa, currently under the control of the Gulf Cartel. Refugio is a rural community not far from Miguel Aleman and Ciudad Mier, near Roma, Texas–an area without any physical barriers and is a drug/human smuggling hotbed.

Tamaulipas Attorney General Irving Barrios Mujica said in a broadcasted interview that the scene of the shootout is referred to as the “Little Border” or “Frontera Chica,” and is known for violent cartel activities.

Authorities believe the cartels used explosives and grenade launchers in the skirmish. One of the vehicles left at the scene was described as a white pickup with Texas license plates and makeshift armored plating. It featured logos to pose as a vehicle used by the Mexican Navy. The Northeast Cartel has a long history of using cloned uniforms and equipment to blame authorities for their atrocities.

Investigators believe grenades and incendiary devices were used by the Northeast Cartel to overwhelm the Gulf Cartel’s armored plating techniques.

The bodies of the 21 cartel gunmen and the burned vehicles were discovered by a Mexican Army squad assigned to Miguel Aleman, information provided to Breitbart News by Tamaulipas law enforcement sources revealed. The soldiers called nonmilitary authorities to report the discovery. A squad of state forensic investigators took custody of the scene to gather evidence and try to identify bodies.