Two Mexican federal police officers allegedly participated in the disappearance of 43 students from a rural teachers’ college in the southwest state of Guerrero in September 2014, the National Human Rights Commission said Thursday, implicating national agents in the case for the first time.

Citing an unidentified witness, the governmental rights body said the federal agents were involved with municipal officers in the disappearance of a group of teacher trainees in the southern city of Iguala.

Prosecutors have already charged municipal police officers in connection with the mass abduction in the southern city of Iguala on September 26-27, 2014.

But the governmental rights commission said it found an eyewitness who saw two federal agents near Iguala’s courthouse, where municipal officers had stopped a bus with 15 to 20 students on board.

The commission also said another local police department, from the town of Huitzuco, had a previously unknown role in the disappearance, which occurred after the students seized buses that were meant to take them to Mexico City to participate in a protest.

Municipal police in Iguala fired on the buses, forcing them to stop, after which the students threw rocks at the officers.

The officers bundled the students into several patrol vehicles, including three from Huitzuco. When the federal officers arrived, they asked what was going on.

An Iguala officer said the students would be sent to Huitzuco, where “the boss” — possibly a drug cartel member — would “decide what to do with them,” the commission said.

The federal officers responded, “Ah, OK, that’s good,” and allowed the local police to take the students away.

José Larrieta Carrasco, a commission member, said his team had corroborated and cross-checked other information in the witness’s account, and come to the conclusion that it was probably “trustworthy and true,” according to Vice News.

Huitzuco would be a new location in the twisting saga, as authorities have maintained that suspects told investigators that the students were killed in the nearby town of Cocula.

The commission said there was enough evidence to “presume the participation of members of the Huitzuco municipal police and two federal police officers” in the disappearance, adding that it has the name of one of the two federal agents, which it gave to prosecutors.

The commission also said a soldier on a motorcycle took pictures of the incident and then left. Families of the victims have called for an investigation into whether the military had a role in the case, but the army denies any wrongdoing.

Troubling questions

The Mexican government’s account of the Ayotzinapa 43 disappearance, as the crime has come to be called, has been called into question by numerous sources.

A report by an Argentine forensics team released in February said that the garbage dump in Cocula — where government investigators said the students’ bodies were incinerated — contained the remains of 19 people, none of whom were 43 students abducted in Iguala.

While the role of federal-police involvement in the Ayotzinapa 43 disappearance is not confirmed, Mexican police, particularly on the municipal level. have been found to have extensive ties to criminal activity. A federal deputy said in late March that 6,500 police officers were operating a kidnapping operation that ranged across the country.

Allegations of official involvement in the Ayotzinapa 43 disappearance, as well as the government’s much-criticised investigation, have continued to dog the country’s president, Enrique Peña Nieto, whose approval ratings fell to a historic low at the beginning of 2016.

“Peña Nieto doesn’t know how to defend us because he is a donkey,” said Felipe de la Cruz, a relative of an Ayotzinapa student, at an event in New York in mid-2015.

De la Cruz then paused, considering the implication of what he had said. “Please apologise to the donkeys for me,” he added.

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