(Reuters) - Mexican authorities are preparing to arrest dozens of people implicated in the kidnapping and alleged murder of 43 student teachers in southern Mexico more than three years ago, the prosecutor in charge of the case said on Friday.

Prosecutor Alfredo Higuera told a hearing of the Inter-American Commission on Human Rights (IACHR) in Bogota he had obtained new information to file charges against 30 people, including local police officers.

The disappearance of the 43 student teachers on Sept. 26, 2014, in the city of Iguala in Guerrero state sparked international outcry, battering Mexico’s reputation and undermining the popularity of President Enrique Pena Nieto.

Guerrero has become Mexico’s deadliest state as a growing number of gangs battle over the control of poppy fields used to produce opium, the main ingredient in heroin.

An initial investigation by the government stated that the 43 were abducted by corrupt police who handed them over to members of a local drug cartel, who then killed them, incinerated their bodies at a trash dump and threw the ashes into a river.

However, an international team backed by the IACHR uncovered irregularities in the case that undermined the conclusions of the official investigation.

Higuera launched a new probe in 2016, and he said Friday that he had developed new lines of investigation.

Later on Friday in a radio interview, Higuera said he had ruled out a theory that the students, who had commandeered buses to drive into the Mexican capital for a protest, had unknowingly taken a bus with a hidden heroin shipment.

Mario Patron, director of the Miguel Agustin Pro Juarez Human Rights Center (Centro Pro) that represents family members of the missing youths, told the IACHR that there are doubts about the progress of the new probe.

He said that no new charges had been filed since December 2014.