A federal judge has ordered that the Attorney General’s office (PGR) reopen the case of the 2014 Tlatlaya massacre, ruling that the original investigation lacked due diligence.

According to a statement issued by the human rights advocacy group Centro Prodh, Judge Erik Zabalgoitia Novales ruled on May 25 that the investigation carried out by PGR was not exhaustive, adequate or effective, and ordered a series of actions to clarify the case and establish responsibilities.

It remains unclear why it took nearly three months for the order to be made public.

There was evidence from the start of a cover-up in the June 2014 shooting in which soldiers gunned down 22 civilians in a warehouse in the municipality of Tlatlaya, México state. It was initially described as a clash with a group of armed criminals who allegedly opened fire on an army patrol.

The details of what actually happened began to surface after the Associated Press found discrepancies at the crime scene. A witness later confirmed a reporter’s suspicion that the scene had been altered by army personnel.

The National Human rights Commission (CNDH) later determined that between 12 and 15 of the victims did not die in a gunfight, as officials had stated, but were arbitrarily executed.

“Due to this faulty investigation, to this date there is not a single person that has been held accountable, as [the PGR] did not present enough evidence to individually single out those responsible,” said the document issued by Centro Prodh.

“This lack of due diligence is one of the many forms taken by the unacceptable covering-up of serious human rights violations in Mexico,” concluded the statement.