The Office of the U.N. High Commissioner for Human Rights says it is "deeply concerned" that nobody has been punished almost two years after soldiers killed 22 suspects in southern Mexico.
Office spokeswoman Ravina Shamdasani yesterday said that the case remains "mired in impunity" and victims continue to be denied justice and the truth.
The office has called for an autonomous forensic institution to investigate such cases.
Last week a civilian court freed the last three soldiers accused of homicide in the 2014 army killings, in which at least a dozen of the suspects were allegedly executed after they surrendered.
The court said there was a lack of proof of charges of homicide, cover-up and alteration of evidence.Prosecutors have said they will offer additional evidence.
