Three Mexican farming activists from among a group of eight people who went missing last week have been found brutally murdered, authorities said Monday. Authorities found the three in Guerrero state, apparently beaten to death along a highway on Monday, friends and a survivor of a botched kidnapping said. Another four of the eight men who apparently were abducted escaped early Monday, while the last man in their group remained missing, one of those who escaped told local media. Last Thursday, members of the Emiliano Zapata Farmers' Union blocked a highway in Iguala demanding that the government give them fertilizer. Hours later, their families reported the eight missing. The three bodies were located at a rest stop along an old highway that runs from Mexico City to Acapulco near the town of Tepecoauilco. Guerrero, one of Mexico's poorest states, this year emerged as a new tinderbox of social conflict and violence linked to drug cartels. In April, Guerrero officially authorized vigilante groups that emerged this year to defend communities against violent drug gangs. The vigilante movement began in the municipality of Ayutla de los Libres and then spread elsewhere, as state and federal authorities tolerated their presence in towns where local police have failed to rein in gangs.