Mexico City, Mexico - Twelve years after the disappearance of dozens of Mexican students from a rural university, allegedly at the hands of drug traffickers and police, authorities said Monday that they had identified 17 new suspects.

Thousands of people attended an annual march on Saturday in Mexico City to demand justice for 43 young men who were studying to be rural teachers in Ayotzinapa, in the violence-hit state of Guerrero.

The students were traveling from Guerrero to a protest in Mexico City on September 26, 2014, when police stopped them in the town of Iguala.

The investigation suggests that the police handed the students over to a local cartel.

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Dozens of arrests have been made, but so far, no one has been convicted in an affair that traumatized Mexico and stained the country's reputation.

Only three bodies have been recovered.

Mauricio Pazaran, the special prosecutor in charge of the investigation, said that a new analysis of phone calls made on the night of the students' disappearance had led to the arrests of 17 new suspects.

He said the analysis had revealed communications between public officials, police officers, individuals linked to organized crime groups, and private citizens.

He added that at a funeral home, investigators found an illegally obtained weapon, a bone, and unregistered bone fragments and teeth.

He said that a public employee and a municipal police officer had used the cell phones of two students days after their disappearance.

One of the new witnesses "participated directly in the events, but was a minor at the time," he added.

The minor, who was arrested in April, is a member of the Guerreros Unidos cartel, the prosecutor said.

He noted that 168 people are being prosecuted in the case, 130 of whom were in pretrial detention.

Mexico has been plagued by cartel violence that has killed or left missing over half a million people in just a few decades, according to the government's own estimates.