An anonymous source told the independent website FARC commanders sold their interests in the drug trade to the Mexican Sinaloa cartel Wednesday.
The sales may extend the reach of the cartel into Colombian territory.
InSight Crime, the Latin American organized crime watchdog, said the sales may indicate FARC rebels may feel they can attain peace with the Colombian government.
The cartel already operates cocaine laboratories in Colombia and has a growing presence in the country, Colombia Reports said.
Colombian President Juan Manuel Santos asked for an investigation into Sinaloa Cartel activities in February, Colombia Reports said.