Prosecutors in the Mexican state of Guerrero said Friday they have formally charged former Iguala Mayor Jose Luis Abarca in the disappearance of 43 students.

Abarca is described as the "probable mastermind" in the September 26 disappearance of the students. He is charged with six counts of aggravated homicide and one count of attempted homicide, the state attorney's office said.

Authorities said the students -- mostly men in their 20s studying to be teachers -- were abducted by police in September at Abarca's direction. Police killed some students, and the rest are believed to have been turned over to gang members to be executed, Mexican Attorney General Jesus Murillo Karam has said.

The men's bodies were burned, and some remains were thrown in a river.

The students were traveling to Iguala to protest a lack of funding for their school.

Officials have said that Abarca ordered the city's police chief to stop the demonstration out of concern it would disrupt one of his own events.

In all, at least 74 people have been arrested in connection with the disappearances and deaths, which have sparked huge protests across Mexico.

The governor of Guerrero has taken a leave of absence after being criticized for failing to act quickly enough in the matter.

(CNN)