The leader of a Mexican drug cartel has been arrested along with dozens of police officers believed to be involved in the disappearance of 43 trainee teachers.
Sidronio Casarrubias Salgado who heads the Guerreros Unidos gang was detained on a motorway leaving Mexico City.
The college students were last seen three weeks ago being bundled into police vehicles in the city of Iguala, half way between Mexico City and Acapulco.
They had earlier been at a rally where there were clashes with police and masked men.
The town’s mayor and his wife are also being sought by police.
Thousands of people have held demonstrations across Mexico demanding to know the whereabouts of the students.
One protester at a rally in Acupulco said: “People are fed up and the drug gangs have already infiltrated all government institutions. They are in charge, they say what what happens or what doesn’t.”
While searching for the students, police discovered an unrelated mass grave with 28 bodies.
Protesters fear the students were murdered by police working on behalf of gang members.