Authorities in Mexico have charged seven police officers with torturing three women who witnessed a deadly incident in the town of Tlatlaya.
In 2014 soldiers opened fire on a group of people in a warehouse in the town, in Mexico state, killing 22.
The women claim the officers tortured them to force them to back the army's version of what happened in Tlatlaya.
The soldiers had said those killed died in a shoot-out, but an investigation concluded many were executed.
The confrontation happened on 30 June 2014 near the village of San Pedro Limon, about 240km (150 miles) south-west of the capital, Mexico City.
An army patrol reported being shot at and chasing the attackers to the warehouse.
The soldiers said 22 suspects, reportedly members of a drug cartel, were killed in the shoot-out which ensued.
But the fact that only one police officer was injured in what had been described as a fierce and long gun battle raised suspicions.
Investigators said that the pattern of bullet holes in the warehouse suggested many of the victims had been lined up against a wall and shot at close range.
Mexico's Human Rights Commission, an official government body, concluded in its report that at least 12, but possibly up to 15 of the victims had been executed in the warehouse.
Three women who were in the warehouse survived. One of them said most of those killed had been shot in cold blood.
The witnesses said they were threatened and tortured by police officers questioning them about the events, and told to back the army's claims.
Apart from the seven police officers charged with torture on Wednesday, three soldiers were charged with murder and seven with breach of duty last year.
None of the cases has so far gone to trial.
According to a report by human rights organisation Amnesty International, torture is rife in Mexico and is routinely used by the security forces to extract confessions.