Colombian government forces dismantled a massive synthetic drug lab allegedly used by the Revolutionary Armed Forces of Colombia (FARC) to finance insurgent operations. The army uncovered the secret laboratory Tuesday in the rebels’ stronghold of Putumayo in southwest Colombia. It’s the first time a synthetic drug lab apparently run by FARC has been found in that part of the country, Agence France-Presse reported, citing military sources.

“This discovery indicates this terrorist group is implementing a new kind of criminal operation to obtain illegal financing,” the Colombian army said in a statement Tuesday.

Military intelligence officials told AFP the drugs produced in the secret lab were sent to the Sinaloa cartel, one of the main drug gangs in Mexico. The lab was equipped for about 30 workers and capable of producing 3 tons of cocaine and synthetic drugs per month. “That amounts to about 30 billion pesos [$11.7 million] a month,” Colombian army Gen. Alfonso Vaca told AFP. “It is a major blow to the FARC’s logistical and financial structure.”

Colombia once supplied about 90 percent of the world’s cocaine, but the country now vies for the top spot with Peru, which has re-emerged as a major producer. Nevertheless, drug trafficking continues to be a vital source of funding for FARC, a Marxist guerrilla group that has sustained decades of violent conflict with successive Colombian governments. Humberto de la Calle, Colombia’s chief peace negotiator, has called the illegal drug trade “the fuel that feeds the conflict.”

FARC was established in the 1960s as the military wing of the Colombian Communist Party following attacks on rural communist territories by the right-wing Colombian army. To fund the expansion of its forces, FARC began taxing drug producers and smugglers in 1982. Today, FARC’s massive drug profits help purchase weapons, uniforms and supplies to recruit fresh fighters. What began as a band of farmers who fled political violence has burgeoned into a leftist guerrilla organization that is now Latin America’s oldest and largest rebel army.

“Although the illegal drug industry began taking hold in Colombia in the 1970s, the FARC had long considered the business counterrevolutionary and feared drug money would corrupt its forces. But as a rural-based rebel movement with few ties to urban areas, money was always in short supply,” Colombian journalist John Otis wrote in a paper published by the Wilson Center’s Latin American Program, a think tank based in Washington.

The warring sides have been in negotiations to end the conflict since 2012. Peace talks in Cuba have focused on efforts to turn the rebels from “an adversary that profits from drug trafficking” into “part of building the solution,” Colombian President Juan Manuel Santos said. But the Colombian government and FARC have not yet reached a deal to end the five-decade conflict that has killed 220,000 people, AFP reported.

Santos resumed military operations against the guerrillas last month after FARC broke a unilateral ceasefire and attacked government forces in the Cauca region of southwest Colombia. The suspended truce and the resumption of airstrikes have jeopardized the peace process.