Nine people were killed and eight others suffered severe burns on Friday after an explosion at a clandestine cocaine production laboratory near Colombia’s border with Ecuador, local authorities said.

Preliminary investigations indicated that the blast was caused by the explosion of a gas cylinder during drug manufacturing operations. The laboratory was located on land belonging to the Indigenous Awa people in Nariño province in southwestern Colombia, a region considered a major hub for cocaine production and marked by the presence of armed rebel groups.

Police Colonel John Jairo Uría said in a video statement that “the incident occurred at dawn on January 23.” He added that the victims were working for a dissident group that split from the Revolutionary Armed Forces of Colombia (FARC) and rejects the 2016 peace agreement with the government.