A panel of international experts have accused Mexico's government of undermining their probe into the fate of 43 trainee teachers apparently massacred in 2014, the most notorious human rights case in Mexico in recent years.
The independent panel on Sunday (local time) said the government's stonewalling has stopped them from reaching the truth as they wrap up their work and prepare to leave Mexico.
The attorney general's office, they said, did not let them re-interview detainees accused of the crime or obtain other information in a timely fashion. Prosecutors did not pursue investigative angles that the experts suggested.
"The delays in obtaining evidence that could be used to figure out possible lines of investigation translates into a decision (to allow) impunity," the report by the experts, commissioned by the Inter-American Commission on Human Rights (IACHR), said.
The case has drawn international attention and stirred protests and outrage in Mexico, where violence has surged in a decade-long drug war. Lawlessness reigns in parts of the country and has tarnished President Enrique Pena Nieto's reputation.
At a two-and-a-half hour news conference on Sunday attended by more than 1,000 people, the experts cast doubt on aspects of the government's version of events and said they had been repeatedly blocked in their efforts to obtain evidence from Mexican authorities.
As the experts finished their remarks at the news conference, audience members yelled, "Don't leave!"
Mexico's government says that corrupt police in late 2014 handed the student teachers in the southwestern city of Iguala over to drug gang henchmen, who believed the trainees had been infiltrated by a rival gang. They then incinerated them at a garbage dump in the southwestern Mexican state of Guerrero.
While the experts' probe showed the municipal police were mainly responsible for the disappearance of the students, they said the federal police should also be investigated.
One of the experts, Carlos Beristain, also said detainees in the case showed signs of torture.
The remains of just one of the 43 students has been identified from a charred bone fragment. The government said it was found in the Rio San Juan, a river by the town of Cocula, near Iguala where the students disappeared.