Mexico's President Enrique Peña Nieto addresses the 69th United Nations General Assembly at U.N. headquarters in New York, Sept. 24, 2014. His government is investigating whether eight Mexican army soldiers killed 22 gang members in an alleged massacre. Reuters

At least eight Mexican army soldiers have been detained in a military prison in Mexico City over the shooting deaths of 22 gang members in an alleged massacre in rural Mexico. The 22 victims were allegedly surrendering when they were executed. The Mexican army soldiers face charges of disobedience, dereliction of duty and military discipline in the high-profile case.

Military officials insist the 22 suspects died after firing first from a warehouse as the Mexican army soldiers patroled the street. But only one soldier was wounded in the alleged gunfight and witnesses have told reporters that the soldiers killed the suspects after they surrendered. The suspects were then allegedly lined up and shot dead.

The state of Mexico prosecutors' office released a statement in July saying there was "no evidence at all of possible executions." The office said it found ballistic evidence of "crossfire with a proportionate interchange of gunshots," according to the Associated Press.

The alleged massacre, if confirmed, would be the worst committed by the Mexican army since President Enrique Peña Nieto took office in December 2012. His predecessor, Felipe Calderón , was hounded with allegations of torture and other abuses against drug cartels across Mexico. The recent army shooting allegedly occurred on June 30 in Tlatlaya, about 240 kilometers, or 150 miles, southwest of Mexico City.

The U.S. government, which has provided more than $1 billion in training and equipment to Mexico, has called for a "credible review" of the alleged massacre by civilian authorities. Human Rights Watch said the incident could prove to be one of the "most serious massacres in Mexico."

The Mexican Supreme Court has ordered military personnel accused of crimes involving civilians be tried in civilian courts. But the army has been slow to comply, according to the Los Angeles Times. Defense Minister Salvador Cienfuegos Zepeda, an army general, said this week before the arrests of the Mexican army soldiers that "any behavior that distances itself from this principle must be taken to the corresponding judicial courts," according to Agence France-Presse.