Mexico City: Mexican prosecutors will investigate officials who under the previous government handled a "discredited" probe into the 2014 disappearance of 43 student teachers, the attorney general's office says.

The abduction and apparent massacre of the trainee teachers by corrupt police working with a drug gang sparked international condemnation of Mexico and seriously damaged the reputation of then-president Enrique Pena Nieto.

Last week, his successor, President Andres Manuel Lopez Obrador, said the government would file a complaint to the attorney general over the release from prison of one of the main suspects behind the September 26, 2014, disappearances.

A judge ordered the release of Gildardo Lopez Astudillo, the gang leader blamed for ordering the killing of the students, after finding that officials had tortured him to obtain evidence.