A protest to demand justice for 43 Mexican students who disappeared in 2014 turned violent on Thursday, leaving 11 police officers injured, authorities said.

A confrontation took place outside the attorney general’s office in Mexico City after demonstrators gathered, calling for people linked to the case to be arrested.

“Some protesters physically assaulted officers and threw explosive devices at them,” Mexico City’s public security secretariat said in a statement.

“Consequently, 11 police were injured by firecrackers and bruises from blows to different parts of the body,” it said.

The officers were taken to hospital for evaluation and were found to be out of danger, the statement said.

Demonstrators scrawled graffiti outside the attorney general’s office and carried banners demanding the safe return of the students.

So far, the remains of only three victims have been identified.

On Wednesday, relatives of the students protested outside Israel’s embassy, demanding the extradition of Tomas Zeron, a former top investigator wanted in connection with the case.

Zeron is one of the architects of the so-called “historical truth,” the official version of the case presented in 2015 that was rejected by the victims’ relatives and independent experts.

The 43 teaching students had commandeered buses in the southern state of Guerrero to travel to a demonstration in Mexico City before they went missing.

Investigators say they were detained by corrupt police and handed over to a drug cartel that mistook them for members of a rival gang, but exactly what happened to them is disputed.

Last month, a truth commission tasked by the current government to investigate the atrocity branded the case a “state crime” involving agents of various institutions.

The next day, former attorney general Jesus Murillo Karam, who led the controversial “historical truth” investigation, was detained on charges of forced disappearance, torture and obstruction of justice.

Prosecutors said that arrest warrants had been issued for more than 80 suspects, including 20 military personnel, 44 police officers and 14 cartel members.

Read the Latest News and Breaking News here