A Mexican army officer and seven soldiers were detained in connection with the shooting deaths of 22 gang suspects after a witness said 21 of them were executed.
The defense ministry said the officer and the soldiers were taken to a military prison in Mexico City and face dereliction of duty charges in the high-profile case.
"The aforementioned military personnel participated in the events that took place on June 30, 2014, in Tlatlaya," the ministry said in a statement.
The officer, whose rank was not disclosed, also faces charges of violating military discipline and disobedience, the ministry said in a statement.
The ministry indicated that the military charges are separate from any legal action that civilian prosecutors could take in the case.
The federal attorney general\’s office as well as the semiofficial National Human Rights Commission are carrying out their own investigations.
The decision to detain the soldiers marks a reversal from the military\’s initial assessment of what transpired in Tlatlaya, 240 kilometers (150 miles) southwest of Mexico City.
In a statement following the June 30 incident, the defense ministry said the suspects were killed in a shootout after they had shot first from a warehouse at a military patrol.
But the Latin America edition of US magazine Esquire reported last week that it had interviewed a woman who saw the soldiers kill the suspects after they surrendered following the skirmish.
Questions were also raised after the military reported that only one of its soldiers had been wounded in the gunfight.