According to local authorities, the massacre took place in a farm house in Santa Rosa de Osos, a rural municipality in the center of the Antioquia department, approximately 20 miles north of the department capital Medellin.
The municipality’s mayor told radio station Caracol the victims were ordered to gather in a farm after which the perpetrators threw a grenade into the building.
Those who survived the explosion were shot to death, mayor Francisco Jair Palacio told Caracol Radio.
The owners and workers of the farm had received death threats from the “Rastrojos” over extortion payments, Palacio added.
Governor Sergio Fajardo condemned the massacre, adding on Twitter that the fight against drug trafficking organizations “is long.”
Mal día. 10 personas asesinadas en una vereda de Santa Rosa de Osos, ayer en la tarde-noche. Infamia. La batalla contra las Bacrim es larga.
— Sergio Fajardo (@sergio_fajardo) November 8, 2012
The Santa Rosa de Osos massacre is the bloodiest of the year, but came during a time of increased tensions and skyrocketing homicide rates in the north of Antioquia where the Rastrojos and their rivals, neo-paramilitary group the “Urabeños,” are involved in a war over the control of drug trafficking routes.