Hundreds of protesters took to the streets of Mexico City on Saturday to mark the one-year anniversary of the disappearance of 43 students.
Families, friends and supporters of the students have regularly marched to demand that authorities determine what happened to them.
Demonstrators throw stones in clashes with riot police that occurred during the march in Mexico City, Sept. 26, 2015.
The 43 students from a teachers college disappeared September 26, 2014, after a clash with police in Iguala, a city in the southern state of Guerrero. Six other people were killed by police during the disturbances.
Only two sets of remains have been identified so far.
Mexico's former attorney general has said local police illegally detained the students and then turned them over to the local drug gang Guerreros Unidos, which then allegedly killed them and incinerated their remains.
A group of independent experts assembled by the Inter-American Commission on Human Rights took apart that version earlier this month, saying authorities knew who the students were from the minute they headed for Iguala, and at the very least did nothing to stop the attacks.
The experts have suggested that the attack occurred because students unknowingly hijacked a bus carrying illegal drugs or money. Iguala is known as a transit hub for heroin going to the United States.
Mexican President Enrique Pena Nieto met with families of the students Thursday to reassure them that his government had not closed its investigation.
The president also promised to create a new special prosecutor's office to investigate the country's thousands of missing-person cases.
More than 25,000 people disappeared in Mexico between 2007 and July 31, 2015, according to the government.