Thousands of Mexicans are gearing up to stage a nationwide strike to demand justice for the 43 students who went missing more than a month ago at the hands of local police. The 72-hour strike begins Wednesday and ends on Friday.

Wednesday represents Mexican protesters’ third “Global Day of Action” over the missing students since they disappeared on Sept. 26 after a police attack in southern Guerrero state. University students, teachers, families of the disappeared and other supporters are also planning to stage a mass march from the presidential mansion Los Pinos to the main plaza in Mexico City.

Religious and civic groups also gathered in Mexico City’s main square Tuesday night to pray for the missing students. They are planning a 43-hour fast beginning Wednesday evening.

The strike and mass march comes a day after federal authorities announced they had detained the former mayor of Iguala, the town where the students were last seen, after a monthlong search. José Luis Abarca and his wife, María de los Ángeles Pineda, are considered to be the “masterminds” behind the 43 disappearances: Authorities believe Abarca ordered the police to go after the students, fearing they would disrupt a speech being given by Pineda that same day. The police shot at the students, who were taking buses back to their campus, resulting in three deaths.

Investigators accuse the police of then handing the students over to the Guerreros Unidos, a local gang, with whom the police and mayoral couple are suspected of having close ties. Abarca and Pineda fled town immediately after the students first went missing; they had been considered fugitives until their arrests in Mexico City Tuesday.

While federal authorities have also arrested a handful of gang members and dozens of police officers in connection with the disappearances, the actual whereabouts of the students remain a mystery. Last month, investigators found several mass graves on the outskirts of Iguala, containing dozens of charred bodies, but DNA testing found no match with the missing students -- a result that provoked even more outcry from Mexicans over the pervasiveness of violence in Guerrero. Last week, authorities found another mass grave in Cocula, about 10 miles away from Iguala, and DNA testing is still underway.