Colombian police reported breaking up two heroin smuggling rings, pointing to links between major criminal groups and the little-known independent traffickers who handle most of the country’s heroin business.

On May 18, police announced that they had dismantled a heroin trafficking ring in the southwestern province of Nariño, where the majority of Colombia’s opium poppy crops are located, capturing 18 people. Two days later, another round of arrests broke up a separate heroin ring that was based in the northeastern city of Cucuta, in Norte de Santander province, on the Venezuelan border.

The common denominator between the two groups is that a member of each was captured in the town of Buesaco, in the highlands of Nariño on the border with Putumayo province, indicating this may be a major processing or collection center for Colombian heroin. In 2009 police made Colombia’s biggest-ever heroin discovery, seizing a stash of 97.5 kilos in a rural area near Buesaco.

While major criminal gangs control the processing, transport and export of cocaine in Colombia, the heroin business is left mostly in the hands of 28 “mini cartels” made up of as few as 15 people, according to El Tiempo newspaper. These apparently independent gangs do, however, have ties to larger organizations.

Police linked the first ring, led by Juan Carlos Cadena, alias “Manuel Cadena” and Jhon Darwin Pantoja, alias “Negocito,” to the FARC‘s 29th Front and to the Rastrojos criminal network, both of which operate in Nariño. According to police, Cadena provided the FARC with ammunition and weapons in exchange for heroin, while the Rastrojos offered the smugglers security to move the merchandise for shipment to the United States, either on go-fast boats from Tumaco via Central America, or carried by “drug mules” on commercial flights from Cali.

The Rastrojos also provided muscle to Cadena’s band. However, in one incident recounted by police, the Rastrojos kidnapped Cadena in November 2011 and held him for an unspecified amount of time for failing to pay for their services.

Police did not say whether the Cucuta-based gang — led by half-brothers Felix Humberto Celis and Ramon Eduardo Parada — was linked to any of the Colombian criminal world’s major players. But, according to a recent report on criminal activity on the Colombian-Venezuelan border, an alliance between the Rastrojos and the Paisas, working with the Mexican crime syndicate the Zetas, moves heroin along the same trafficking routes used for cocaine shipments from Norte de Santander through Venezuela and the Caribbean.

Colombia’s heroin production plummeted in the past decade, with the area under poppy cultivation dropping from 7,500 hectares in 2000 to just 341 hectares in 2010, the last year for which figures are available, according to the UN Office on Drugs and Crime’s latest report on illegal crops in Colombia.

By contrast, Mexican black tar heroin is flooding the US market, even on the East Coast where Colombian white powder heroin once reigned.

Nonetheless, DEA sources told InSight Crime that the majority of heroin they observe entering the US appears to be Colombian. However, the US Justice Department’s 2011 National Drug Threat Assessment suggests that heroin producers in Mexico may be using Colombian processing techniques to create a white powder form of heroin, which could account for the conflicting information.

Mexico seized 268 kilos of heroin in 2011, and eradicated 4,124 hectares of poppy, the raw material for heroin, according to the latest US International Narcotics Control Strategy Report. The 2011 World Drug Report stated that Mexico’s poppy cultivation was 19,500 hectares in 2009.

As in Colombia, Mexico’s heroin trade is largely controlled by smaller trafficking cells, with the major transnational criminal organizations involved only indirectly. In Mexico, for example, groups such as the Sinaloa and Gulf Cartels charge smaller gangs to use their trafficking corridors and their links in distribution markets such as the US.