The governor of the Mexican state where 43 students vanished following a confrontation with police has resigned.
Guerrero governor Angel Aguirre said he was stepping down to assist the investigation into the disappearances.
Family and friends of the missing students had repeatedly called for the governor to go in the wake of the scandal.
There has been nationwide and international outrage since the disappearance.
"I have decided to take my leave from the state parliament," Mr Aguirre told a news conference.
He said he hoped his decision would create a "political climate which allows attention to these matters and their solution".
Mexican authorities have searched in vain for any trace of the trainee teachers who disappeared on 26 September in the city of Iguala.
On Wednesday, tens of thousands marched through Mexico City and other cities to protest at the disappearance of the students and failure to find them.
Mexico authorities have ordered the arrest of the mayor of Iguala, his wife and an aide, alleging they masterminded the attack, which left six students dead and the 43 missing.
Mr Aguirre did not specify how long he planned to take leave from his post.
He stated only that the regional parliament should choose an individual who "must lead this effort in the coming months".
The next elections for governor in Guerrero state are scheduled for June 2015, meaning Mr Aguirre could theoretically not return to office.
The students' disappearances have shone a light on the murky relationships between corrupt officials, police and drug cartels in Mexico.
Authorities said local officials and police worked closely with the Guerreros Unidos drug cartel in the attack, which could prove to be one of the worst slaughters of Mexico's bloody eight-year drug war.
Authorities have found several mass graves in Iguala but said 28 sets of remains examined so far do not correspond to the students.
