MEXICO CITY (AP) — Decades after Mexico’s “dirty war,” the military has obstructed a government investigation into human rights abuses, the official heading the probe said Wednesday.

Alejandro Encinas Rodríguez, deputy minister for human rights, said at a news conference that investigators withdrew last month after discovering military officials were hiding, altering and destroying documents.

Encinas said some officials’ actions clearly violated a presidential decree granting investigators unfettered access to records.

“As for people who could be criminally prosecuted, or that we already have in our sights to arrest at some point, it is responsible to say we are investigating. As soon as we have any clear indication and evidence, of course we will proceed,” he said.

The Ministry of National Defense did not respond to an email from The Associated Press asking for comment.

The inquiry was established under the Mexican human rights department’s commission for truth in October 2021 to investigate human rights violations during the “dirty war” against leftist guerillas, dissidents and social movements in the 1970s and ‘80s.

During that time hundreds of people were illegally detained, tortured and disappeared by the military and security forces. Over 2,300 direct and indirect victims are still alive today, the inquiry commission said Wednesday.

David Fernández Dávalos, a member of the commission’s subgroup for historical clarification, said the Ministry of National Defense “continues this cycle of impunity, opacity and injustice” by moving, altering or destroying documents.

Fernández told reporters that military officials initially withheld documents they claimed were private for reasons of national security, personal privacy, or “preserving relations” with other countries.

Then he said, “Files that we already knew were composed in a certain way were handed over with sheets out of place and notes ripped out.” Military officials also moved boxes of files so the investigators couldn’t find them and in some cases just flatly denied access to documents, he said.

Calling 2023 a “year of listening,” other members of the inquiry spoke of success visiting military posts and conducting hundreds of interviews with victims.

In June the subgroup for disappeared people uncovered the remains of seven people thought to have been killed in 1971 in the southern state of Guerrero. They have since begun analyzing ocean currents and flight paths to find where corpses dumped in the Pacific by the military’s “planes of death” might be found today.