Mexico City, January 14 (RHC-teleSUR) -- Mexico’s attorney general’s office announced Tuesday that the investigation into the case of the missing 43 Ayotzinapa teachers training college students has gone cold.

“All the investigation leads have been exhausted,” said Director of the Attorney General’s Office Tomas Zeron in a press conference on Tuesday.

Zeron explained that the press conference was called “in order to make public the results of the investigation so far ... as well as to establish and clarify any doubts that could have emerged in the presentation.”

He claimed that 380 people had been arrested and interrogated thus far, including 36 military officials, although there were no direct charges against them.

Investigating officials believe the disappearance of the 43 students on September 26th involved the municipal officials and police of Iguala and Cocula, as well as members of the criminal group United Warriors.

Zeron added that the investigation corroborated the link between Maria de los Angeles Pineda Villa, the mayor's wife, and the criminal group; it also confirmed the implication of Iguala's mayor Jose Luis Abarca, suspected of being responsible for the kidnapping, as well as five municipal police, allegedly responsible for the “homicide or the secret burial” of the students.

​However, the relatives of the 43 doubt the veracity of official investigations and refuse to consider them dead. They are awaiting the results of external forensic investigations.

Among the 30 bodies found in the mass graves, 12 have been identified and will be returned to their families, the attorney general stated.

The students' relatives continue to protest against the national government of President Enrique Peña Nieto, demanding an investigation that provides a more satisfactory answer about the disappeared students.

While the government has been criticized for superficially investigating in order to avoid any implication of national institutions, a report published December 14th by El Proceso contradicted the official account of the events. According to this investigation, based on leaked federal and state (of Guerrero) documents, the federal police did in fact participate in the crime.