Demonstrators in Chilipancingo, Mexico, march while carrying photos of 43 graduate students who were murdered in September. Jorge Dan Lopez / Reuters

Authorities may be one step closer to apprehending the people believed responsible for abducting and murdering 43 college students in the Mexican state of Guerrero. The Associated Press reports that Mexican federal authorities have arrested Miguel Angel Landa Bahena, who has been described as an associate of Gildardo López Astudillo, the gang leader who allegedly ordered the students kidnapped, murdered and then incinerated. Landa Bahena was apprehended in Mexico City after four suspects who were first arrested in October and then again in November, identified him as an accomplice of Astudillo’s.

The arrest is the latest twist in an investigation that began last year, after 43 students from a teacher’s college were rounded up on their way to protest a speech that was being given by Maria de los Angeles Pineda, the wife of Iguala’s then-mayor, Jose Luis Abarca. Pineda and Abarca allegedly made arrangements with local police to round up the protesters, then hand them off to members of Astudillo’s gang, Guerreros Unidos, who murdered the students and then burned their bodies in a mass grave. To date, authorities have only able to correctly identify one of the victims’ bodies.

More than 100 people, including Abarca and members of both the local police and Guerreros Unidos, have been arrested in connection with the deaths, though only a handful of people have been formally charged. In early 2015, Mexican authorities concluded there was sufficient evidence available to charge Pineda on suspicion of being involved in organized crime, though the charges brought against her do not specifically mention the 43 students.

The case set off weeks of protests across Mexico, which has been scarred by drug-related violence for the better part of the last decade. Earlier this year, reports surfaced that the Mexican government reportedly suspected the violence would happen but chose not to prevent it.