Murillo Karam’s management of the students’ case is likely to forever frame his tenure as attorney general. The students went missing on Sept. 26 after municipal police opened fire on them in the southwestern city of Iguala. In January, Murillo Karam announced that the case was closed. In a 63-page report panned by critics for lacking sufficient evidence, Murillo Karam said that the 43 students were kidnapped, assassinated and incinerated by the local drug gang Guerreros Unidos.

Murillo Karam will be transferred to the ministry of agrarian and urban development, the official, speaking on condition of anonymity, said. He will be replaced by Arely Gómez González, a senator from the ruling Institutional Revolutionary Party (PRI).

Mexican Attorney General Jesús Murillo Karam, who was harshly criticized for his handling of the disappearance of 43 students from a teachers college in Guerrero state, will step down, a senior government official said Friday.

One month after 43 students disappeared, schoolmates say government wants to get rid of them and their schools

Relatives and classmates of the students blasted Murillo Karam's investigation. Other critics have called the government's version of events implausible.

Despite the discovery of a series of mass graves during the search for the students, only one set of remains has been matched to a missing student. A forensics team from Argentina who worked on the case questioned those results, saying there were numerous problems with the investigation.

Classmates of the 43 missing students said the government was involved with the disappearance. And they argue it is trying to close the school at Ayotzinapa – where the missing students attended – and other "normal" schools, which provide free education and board for the rural poor to become teachers, because students are taught to question authority.

The disappearance of the "normalistas," as the students are called, has sparked the biggest political crisis of President Enrique Peña Nieto's administration and forced his government to place local police forces under federal control. Millions have marched in Mexico and abroad, calling on the government to return the students alive.

Mexico watchers say Murillo Karam will be remembered for the phrase "ya me cansé," or "enough, I'm tired," words he used to abruptly end a press conference in November regarding the missing students. The utterance sparked outrage in Mexico and was turned into a rallying cry by millions of protesters critical of Mexican government corruption and drug-fueled violence.

With wire services