Nuevo Laredo is the base of Los Zetas , originally the armed wing of the Gulf Cartel ; the two organizations separated in early 2010 and have been fighting for the control of the smuggling routes to the United States . As of 2012 , Los Zetas are thought to be Mexico 's largest criminal organization . Drug violence involving the Sinaloa and Gulf Cartels escalated in 2003 , when the city was controlled by the Gulf Cartel . 2012 has seen an unprecedented series of mass murder attacks in the city between the Sinaloa Cartel and Gulf Cartel on one side and Los Zetas on the other
unprecedented series of mass murder attacks
2012 Nuevo Laredo massacres
Nuevo Laredo