Mexico has charged three of its troops with murder, after a shootout in June, which left 22 suspected gang members dead.
Attorney General Jesus Murillo said the soldiers shot the men "without any justification whatsoever".
The victims are alleged to be members of a notorious criminal organisation called La Familia Michoacana and the army at the time said the men died in a fire fight.
However, some the victims appeared to have bullet wounds in the chest, inconsistent with a shootout.
According to the BBC, witnesses say only one person died in the shootout, while the others were killed after surrendering to the army.
Another seven soldiers and their commander were charged last week with military disobedience and breach of duty related to the shootout.