Sixteen police officers were arrested there Thursday for allegedly serving as accomplices to members of a drug cartel suspected in the slayings, the federal attorney general said in a statement.
Twenty-three of the 145 victims found so far were killed at least a month before drug gangs began kidnapping bus passengers along a dangerous highway that leads straight to the U.S. border, The Associated Press reported, citing Tamaulipas state prosecutors.
"This displays the great rot in our institutions," Mexican poet Javier Sicilia, who is organizing protests against the violence, said Wednesday, according to the Houston Chronicle. "All of us have serious shortcomings and criminal complicities disguised as legality that have plunged us into chaos."
San Fernando, just 90 miles south of Brownsville, Texas, has become a favored trafficking route for drug cartels. Officials discovered 72 bodies near the city last summer, and many were identified as immigrants from Central American countries on their way to the United States.
As with so many of the casualties of Mexico's drug wars, the victims of the latest mass slayings -- who officials say were dragged off buses in late March and murdered by members of Los Zetas, one of Mexico's most powerful cartels -- were not necessarily involved in the drug trade at all.
One woman told the Mexican newspaper El Universal that her husband hasn't been heard from since he boarded a bus from Tamaulipas to the U.S. border March 27, the day of one of the slayings. Isabel Ibarra Vargas said her husband, Gerardo Martinez, had a job lined up in Missouri, and had planned to work there for eight months before returning to Mexico to be with her and their young son. But now, the family fears Martinez never made it past San Fernando. Officials have yet to identify his body.
According to reports in El Universal and other local outlets, the women taken off the buses outside San Fernando were raped as well.
More than 35,000 people are estimated to have been killed in Mexico since 2006, when Calderon launched a controversial war against the cartels.