A former high-ranking Mexican federal police official accused of torturing suspects during an investigation into the 2014 disappearance of more than 40 student teachers has turned himself in, authorities said on Friday.

Carlos Gomez Arrieta, who oversaw the Federal Ministerial Police at the time of the abduction and apparent massacre of 43 student teachers from the Ayotzinapa Rural Teachers’ College, had faced an arrest order since March, the interior ministry said.

Coming just two weeks before the incident’s six-year anniversary, his surrender and detention could mark a step forward in President Andres Manuel Lopez Obrador’s push to resolve a case that became a symbol of Mexico’s failure to tackle violence, corruption and impunity.

Accusations against Gomez include “probable participation” in torture and forced disappearance of some people who were questioned in the probe, the interior ministry said in a statement.

The United Nations human rights office has accused authorities under the prior government of torturing dozens of people in connection with the investigation.

Gomez last year resigned from his then-post in Michoacan state’s police after he was identified in a video that appeared to show police using torture to interrogate a suspect.

Gomez has denied the use of torture.

Felipe De La Cruz, the father of one of the missing student teachers, called on Gomez to break an alleged “pact of silence.”

“We hope that … he can also say where the kids are and who else participated in their disappearance,” De La Cruz said.

Investigators in July found a bone fragment belonging to one of the student teachers, which authorities said could open new leads into the case.

Before that, the remains of just one student teacher had been definitively identified.

Arrest warrants are still pending for over 40 public officials, including Tomas Zeron, the former head of Mexico’s criminal investigation agency.

Reuters