The inspector general opened an investigation on Wednesday into officials present at a river in southern Guerrero state on October 28, 2014, the attorney general's office said in a statement yesterday.
Tomas Zeron, the head of the criminal investigations agency, was led that day by a suspect to the San Juan river, in which the burnt remains of students were allegedly tossed by a drug gang.
Foreign experts who aided the investigation slammed Zeron's conduct, saying his failure to make a written report about the visit, including the discovery of a bone, went against the "minimum international standards of investigation."
The lawyers from Colombia and Chile, along with a Spanish psychologist, called for Zeron's actions to be investigated prior to the official announcement.
Some opposition lawmakers demanded his resignation.
Zeron vehemently denied any misconduct late Wednesday, saying his visit to the river site was legally sound.
He released a video showing that he was indeed at the location with a suspect on October 28 but he said no crucial evidence was found that day.
He said the bone that was discovered turned out to be that of a bird, and that a human bone was only found on October 29.
While the experts say an official picture shows that a bag containing a bone belonging to one student was marked "October 28," Zeron said it was a mistake by a forensic investigator and that the picture's metadata, which cannot be altered, is dated October 29.
Zeron said the presence of two officials from the Office of the United Nations High Commissioner for Human Rights seen near the site in his agency's video showed that he was not hiding anything.
