A Mexican judge on Wednesday ordered a former attorney general to stand trial in the case of 43 students whose murky disappearance in 2014 traumatized the nation.
Jesus Murillo Karam will be tried on charges of forced disappearance, torture and obstruction of justice, the Federal Judiciary Council said after a court hearing in Mexico City.
He is considered the architect of the so-called "historical truth" version of events -- presented in 2015 by the government of then-president Enrique Pena Nieto -- that was widely rejected, including by relatives.
So far the remains of just three of the students from the Ayotzinapa teachers' college in the southern state of Guerrero have been identified.
Murillo Karam, a former heavyweight of the once-dominant Institutional Revolutionary Party (PRI), is the most senior figure charged so far in connection with the case, which triggered international condemnation.
He was arrested on Friday at his home in an exclusive neighborhood of Mexico City and remanded in custody.
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President Andres Manuel Lopez Obrador said on Wednesday that anybody involved in a cover-up must be held to account, including the person who "gave the order."
Arrest warrants were also issued last week for more than 80 other suspects, including military personnel, police officers and cartel members, prosecutors announced.
The case is one of the worst human rights tragedies in Mexico, where a spiral of drug-related violence has left more than 100,000 people missing.
The students had commandeered buses to travel to a demonstration in Mexico City before they went missing.
Investigators say they were detained by corrupt police and handed over to the Guerreros Unidos drug cartel, which mistook them for members of a rival gang, but exactly what happened to them is disputed.
According to the official report presented in 2015, cartel members killed the students and incinerated their remains at a garbage dump.
Those conclusions were rejected by independent experts and the office of the United Nations High Commissioner for Human Rights, as well as the families.
Lopez Obrador said in March that navy members were under investigation for allegedly tampering with evidence, including at the dump.
On Thursday, a truth commission investigating the atrocity branded the case a "state crime" involving agents of various institutions.
It said that military personnel bore "clear responsibility," either directly or through negligence, contrary to the "historical truth," which did not attribute any responsibility to members of the armed forces.
The PRI, now an opposition party, has criticized Murillo Karam's arrest as politically motivated.
Mexico has also repeatedly asked Israel to detain the fugitive former head of the Criminal Investigation Agency, Tomas Zeron, in connection with the case.
Zeron is accused of using torture to extract supposed confessions from suspects, enforced disappearance and embezzling public funds.