Colombia’s Rastrojos gang now dominates the Venezuelan border, working with the Mexican Zetas to control much of the drugs moving into this crucial transit nation, according to a new report from a Colombian think tank.

The new report by Corporacion Nuevo Arco Iris said that the Rastrojos were of greater importance in the drug trade than the Marxist rebels who have made the frontier area one of their strongholds. Venezuela is the main transit point for Colombian cocaine heading to market in the United States and Europe, with an estimated 200 tons of the drug passing through every year. While Colombian officials often blame the increased trans-border trafficking on the Revolutionary Armed Forces of Colombia (FARC) and National Liberation Army (ELN), the report’s author, Ariel Avila, said they were “minor players.”

A two-year field investigation found that while the FARC and the ELN maintain a strong presence straddling the 2,000 km-long border, the Rastrojos criminal syndicate is the predominant player in the region. But, while this may be true in terms of the drug trade and other illegal activities, it is highly unlikely that the Rastrojos have more men on the ground than either the ELN or the FARC.

The report said the Rastrojos control the Venezuelan state of Zulia, including the city of Maracaibo, together with Mexico’s Zetas drug gang. If true, it would be the first evidence of the Rastrojos, who have worked with the Sinaloa Cartel to traffic drugs via the Colombian Pacific, dealing with Sinaloa’s arch rivals, the Zetas. This would be further confirmation of the Rastrojos’ business ethic of striking up alliances with whoever best suits their needs. Avila said the Zetas-Rastrojos alliance was established in 2010 when the Mexican drug trafficking organization sent emissaries to the Venezuelan city of Maracaibo.

Initially, the alliance sent drugs from La Guajira in northwest Colombia to Venezuela’s Isla Margarita and then to Jamaica, from where it would be shipped either to Mexico and the United States or Britain and the Netherlands, according to the report. However, researchers found evidence of a recent shift, with drugs moved from La Guajira to Colombia’s San Andres Island, off the coast of Nicaragua, and then through Honduras, Guatemala and Mexico to the United States. The coalition also uses the Port of Maracaibo and clandestine airstrips in Zulia to send drugs abroad, the report said.

Rival network the Urabeños, the other major Colombian criminal syndicate run by former mid-level paramilitary commanders, is allegedly working with Mexico’s Sinaloa Cartel and the Familia Michoacana, as well as Dominican traffickers, sending drugs to the United States from La Guajira via the Dominican Republic, Nicaragua, Honduras, Guatemala and then Mexico. Another route under their control goes through Puerto Rico or the Bahamas and then directly to the Unites States, said the report. The Urabeños, based on Colombia’s Caribbean coast, have been known to sell product to the Gulf Cartel, a former rival and now ally of the Sinaloa Cartel.

Both of the major alliances have infiltrated local officials, with the Rastrojos/Zetas maintaining strong connections to the Colombian National Police and the Zulia State Police, while the Urabeños/Sinaloa group are linked to members of Venezuela’s national guard, according to the investigation, whose findings are published in a voluminous and at some points unwieldy book “The Hot Border Between Colombia and Venezuela.”

Still, the report recognizes the guerrillas as a significant force on the border. The FARC’s two senior leaders, commander in chief Rodrigo Londoño, alias “Timochenko,” and Luciano Marin Arango, alias “Ivan Marquez,” are both believed to reside along the border. Many of the FARC’s units took refuge in Venezuela at the height of the military offensive against them in the last decade, but have recently been returning to Colombia. In part this is the effect of improved bilateral relations: the Chavez government has either run the rebels out or convinced them to leave. Instability on the Venezuelan side caused by Rastrojo-Urabeño clashes has also made the area less hospitable, the Arco Iris report said. The ELN maintain significant control in the northern part of the Colombian province of Arauca and the southern part of the Venezuelan state of Apure, where the ELN reached a non-aggression pact with the FARC in 2010, according to the report. Both rebel groups have influence in coca growing areas, where they protect crops.

Gasoline smuggling is another important illegal activity on the border that has attracted guerrillas, criminal gangs and independent actors. Gasoline in Venezuela costs as little as 18 cents per gallon, while in Colombia a gallon can cost as much as $5. The report calls gasoline smuggling “perhaps one of the most profitable markets on the border.”

All these groups — guerrillas, drug trafficking organizations and gasoline smugglers alike — have managed to co-opt local officials and law enforcement. The report describes how a truck driver smuggling gasoline across the border into Colombia has to pay bribes to the Venezuelan National Guard at one roadblock, then, on the Colombian side, bribes at every police roadblock on the way to Santa Marta. Even more troubling is the finding that Venezuelan military may actually be taking over some drug trafficking routes. The Nuevo Arco Iris investigation found indications that what is known as the Cartel de los Soles (Cartel of the Suns), made up of corrupt elements in the Venezuelan miitary, is not just facilitating drug trafficking, but may in some cases have taken it over from Colombian organizations. It suggests that the November 2011 capture in Venezuela of one of Colombia’s top drug bosses, Maximiliano Bonilla Orozco, alias “Valenciano,” was more a move to eliminate the competition than to put a bad guy behind bars. Bonilla headed factions of the Oficina de Envigado in Medellin and the Paisas along the coast.

The border between Colombia and Venezuela has long been a volatile area, and the presence of guerrilla rearguard camps in Venezuela prompted a tense diplomatic standoff between the two countries in 2010, toward the end of Alvaro Uribe’s presidency. Relations have vastly improved under President Juan Manuel Santos, and talk of the clandestine camps has faded away. But, given the fast-moving reconfiguration of organized crime alliances along the border that is described in the report, both countries will have to turn their attention to the area to combat what the report calls a “mafia state” on the frontier.