In one of his first moves in office, Mexican President Andrés Manuel López Obrador signed an order to form a truth committee to look into the disappearance of 43 students.
The group of students training to become teachers went missing in 2014 in the state of Guerrero.
Students who were able to escape told reporters that corrupt police officers raided buses they were riding in. The students were believed to be kidnapped and then killed.
For years, the families of those students have criticized the government's handling of the investigation.
Under former President Enrique Peña Nieto's leadership, a government report claimed the students' bodies were burned in a fire at a garbage dump.
But independent investigators say there is no evidence to support that claim.
López Obrador said he said he hopes for truth and justice, and to set an example so "never again human rights are violated in our country, so that no other Mexican suffers the disappearance of their children."
Mexico's Undersecretary of Human Rights, Population and Migration will lead the truth committee. The parents of the missing students will be a part of the committee, as well as their lawyers.