Mexican officials said Tuesday that they filed an arrest warrant against Jose Luis Abarca, the former mayor of Iguala in southwest Mexico, for kidnapping 43 students last year. Tomas Zeron, director of criminal investigations at the federal attorney general's office, said, according to Reuters, that officials had also obtained arrest warrants against 44 other people.

The warrant against Abarca becomes the first time the Mexican judicial system has officially linked the mayor with the case of the missing students. However, formal charges have not yet been filed, The Associated Press reported. Abarca and his wife, Maria de los Angeles Pineda, have been in police custody since November, when they were detained in the outskirts of Mexico.

Zeron did not confirm when the warrant was obtained, but it comes after accusations from authorities that the couple has been the mastermind behind the kidnappings, Reuters reported. Authorities also alleged that the couple handed the students over to the Guerreros Unidos drug gang, which reportedly killed and burnt them.

Pineda was charged with organized crime and money laundering earlier this month. Prosecutors had also said that her brothers were leading members of the drug gang.

The 43 students went missing on Sept. 26 and their disappearance had led to nationwide protests, with many demanding the resignation of President Enrique Pena Nieto. In December, authorities confirmed that the DNA of one of the missing students had matched the sample collected from a bone found in a pile of remains in Cocula, in the southern Mexican state of Guerrero.

Abarca is suspected of ordering the police to kidnap the students because they may have disrupted a speech his wife was giving and wanted police to "teach them a lesson," according to Mexican news reports, citing the national investigation. According to reports at the time, police officials shot and killed three of the students and handed over the rest to the gang.