Investigators carry away one of thousands of victims of Mexico's drug war. Photo: Proceso

Washington, DC, December 22, 2014 – With the Mexican government facing widespread public outrage over the alleged role of police and other officials in the September forced disappearance of 43 students, and the killings of at least six others, from Ayotzinapa Normal School, the country’s federal prosecutor (PGR) has for the first time declassified a document on the suspected participation of police in the kidnapping and massacre of hundreds of migrants in San Fernando massacres of 2010-11.

The new revelations, along with key U.S. documents on how violent drug cartels gained control of local police forces in parts of Mexico during the last decade, are the subject of “San Fernando-Ayotzinapa: las similitudes” (“San Fernando-Ayotzinapa: the similarities”), an article published online today in Mexico’s Proceso magazine in collaboration with Michael Evans and Jesse Franzblau of the National Security Archive.

According to declarations from members of the Los Zetas drug cartel named in the newly-declassified “Tarjeta Informativa” (“informative note” or “information memo”), the police acted as “lookouts” [“halconeo”] for the group, helped with “the interception of persons,” and otherwise turned a blind eye to the Zetas’ illegal activities.

Those crimes included the summary execution of 72 migrants pulled from intercity buses in San Fernando in August 2010 and an untold number of similar killings that culminated in the discovery, in April 2011, of hundreds more bodies in mass graves in the same part of the Mexican state of Tamaulipas. The victims were mainly Central American migrants making their way to Texas, which borders Tamaulipas to the north. The state’s highways are at once primary avenues for migrants and highly-contested narcotrafficking corridors.