The Mexican Defense Department says an army officer and seven soldiers are being detained in connection with the June killing of 22 people in rural southern Mexico, an incident the military initially reported as a firefight between criminals and troops, but which a witness later described as a massacre. The department said the eight were involved in the June 30 incident in San Pedro Limon, but gave no specifics. The men were being held in Mexico City on charges of crimes against military discipline, disobedience and dereliction of duty. The military said the charges are being pursued separately from civil investigations. The federal Attorney General's Office is conducting a criminal probe into the killings.