A suspected drug cartel boss allegedly linked to the disappearance a decade ago of 43 college students was arrested in Mexico after being released from prison in 2019, authorities said Friday.

Gildardo Lopez Astudillo, alias “El Gil,” is an alleged leader of the Guerreros Unidos cartel, accused of being behind the disappearance and suspected murders of the students from Ayotzinapa teachers’ college in 2014.

Lopez Astudillo had been arrested in September 2015 in the southern city of Taxco, Guerrero state, about 21 miles north of the town of Iguala from where the students vanished.

“Gildardo Lopez Astudillo was detained,” a federal security source with knowledge of the case told reporters Friday, asking for his name not to be used because he was not authorized to speak to media.

Lopez Astudillo had been transferred to the Altiplano maximum security prison in Mexico state, the source said.

He was arrested on charges of “organized crime,” although the investigation could be expanded, the source said.

In September 2014, the 43 students had been traveling to a political demonstration in Mexico City when investigators believe they were kidnapped by the drug cartel in collusion with corrupt police.

The exact circumstances of their disappearance are still unknown, but a truth commission set up by the government has branded the case a “state crime,” saying the military shared responsibility, either directly or through negligence.  

Arrests have been made or ordered for dozens of suspects, including military personnel. In 2022, federal agents arrested former Attorney General Jesus Murillo Karam, who oversaw the original investigation. 

Lopez Astudillo was released in 2019 — a move condemned by family members of the missing students — after a judge found the evidence against him was obtained illegally.

His arrest comes as relatives are preparing demonstrations to mark the anniversary of the students’ disappearance.

The 43 missing male students are believed to have been killed and burned by drug gang members.

Authorities have been able to identify burned bone fragments of only a few of the 43 missing students. The work largely involves searching for clandestine body dumping grounds in rural, isolated parts of the state where drug cartels are active. In October, officials conducted DNA tests to determine if some of the students were among 28 charred bodies found in freshly covered mass graves.