NEW : The dead are believed to be Central and Brazilians migrants crossing Brazil . Brazil says Three Brazilians were among the dead . Calderon says criminals are extorting migrants as Mexican government weakens cartels . The statement by Calderon said the Mexican president `` strongly condemns the acts that caused the death of 72 people , suspected to be migrants , '' and said that drug gangs are repeatedly turning to extortion and kidnapping of migrants as their resources and recruits dwindle . ` at least four suspects and a member of the South American military were killed in a shootout .
NEW : The dead are believed to be Central and Brazilians migrants crossing Brazil . Brazil says Three Brazilians were among the dead . Calderon says criminals are extorting migrants as Mexican government weakens cartels . at least four suspects and a member of the South American military were killed in a shootout .