MEXICO CITY (AP) — Mexican authorities have arrested a retired general and three other members of the army for alleged connection to the disappearance of 43 students in southern Mexico in 2014, the government announced Thursday.

Assistant Public Safety Secretary Ricardo Mejia said that among those arrested was the former officer who commanded the army base in the Guerrero state city of Iguala in September 2014, when the students from a radical teacher’s college were abducted.

Mejía said a fourth arrest was expected soon, and later a government official with knowledge of the case who spoke on condition of anonymity to discuss the matter confirmed that another member of the army had been arrested.

Mejía did not give names of those arrested, but the commander of the Iguala base at that time was José Rodríguez Pérez, then a colonel. Barely a year after the students’ disappearances and with the missing students’ families already raising suspicions about military involvement and demanding access to the base, Rodríguez was promoted to brigadier general.

The government official who spoke on condition of anonymity confirmed that Rodríguez was arrested and said he was being held at a military installation. The source would say about the others arrested only that two were officers and the third was an enlisted soldier.

Last month, a government truth commission re-investigating the case issued a report that named Rodríguez as being allegedly responsible for the disappearance of six of the students.

Interior Undersecretary Alejandro Encinas, who led the commission, said last month that six of the missing students were allegedly kept alive in a warehouse for days then turned over to Rodríguez who ordered them killed.

The report had called the disappearances a “state crime,” emphasizing that authorities had been closely monitoring the students from the teachers’ college at Ayotzinapa from the time they left their campus through their abduction by local police in the town of Iguala that night. A soldier who had infiltrated the school was among the abducted students, and Encinas asserted the army did not follow its own protocols and try to rescue him.

“There is also information corroborated with emergency 089 telephone calls where allegedly six of the 43 disappeared students were held during several days and alive in what they call the old warehouse and from there were turned over to the colonel,” Encinas said. “Allegedly the six students were alive for as many as four days after the events and were killed and disappeared on orders of the colonel, allegedly the then Col. José Rodríguez Pérez.”

Numerous government and independent investigations have failed to reach a single conclusive narrative about what happened to the 43 students, but it appears that local police pulled the students off several buses in Iguala that night and turned them over to a drug gang. The motive remains unclear. Their bodies have never been found, though fragments of burned bone have been matched to three of the students.

The role of the army in the students’ disappearance has long been a source of tension between the families and the government. From the beginning, there were questions about the military’s knowledge of what happened and its possible involvement. The students’ parents demanded for years that they be allowed to search the army base in Iguala. It was not until 2019 that they were given access along with Encinas and the Truth Commission.

Shortly after the truth commission report, the Attorney General’s Office announced 83 arrest orders, 20 for members of the military. Then federal agents arrested Jesús Murillo Karam, who was attorney general at the time.

Doubts had been growing in the weeks since the arrest orders were announced because no arrests had been announced. The administration of President Andrés Manuel López Obrador has also formed a closer public bond with the military than any in recent memory.

The president pushed to shift the newly created National Guard under full military authority and his allies in congress are trying to extend the time for the military to continue a policing role in the streets to 2028.

On Thursday, Mejía also dismissed any suggestion that José Luis Abarca, who was mayor of Iguala at the time, would be released from prison after a judge absolved him of responsibility for the student’s abduction based on a lack of evidence. Even without the aggravated kidnapping charge, Abarca still faces other charges for organized crime and money laundering, and Mejía said the judge’s latest decision would be challenged. The judge similarly absolved 19 others, including the man who was Iguala’s police at the time.

The Miguel Agustin Pro Human Rights Center and other nongovernmental organizations that have supported the families of the students said in a joint statement Thursday that the government had so far not notified the families of the case against Rodríguez nor the charges he would face.

They said that if the prosecution of Rodríguez did advance on “solid evidence” it could be very relevant for holding the military accountable. The statement noted that there was “abundant” evidence about the collusion of soldiers from the Iguala base with organized crime.

The organizations also called on authorities to appeal the judge’s decision absolving Abarca and others. They said the ruling was the result of poor work by the Attorney General’s Office that originally brought the charges, including the extensive use of torture which led much of the evidence to be excluded.