An army officer and seven soldiers who face disciplinary action for their participation in the killing of 22 people in rural southern Mexico belong to an army battalion with a history of incidents.

The Mexican Defense Department said the eight were involved in the June 30 incident in San Pedro Limon, an encounter that the military initially reported as a shootout but that a witness has described as a massacre.

They belong to the 102nd Infantry Battalion of the 22nd Military Zone in Mexico state, according to media reports and two people with knowledge of the case who spoke on condition of anonymity because they weren't authorized to speak to the press. The battalion is based in San Miguel Ixtapan in the remote southwestern part of the state, about an hour's drive north of where the killings happened.

The area is said to be controlled by La Familia cartel, though it is also land where rival drug gangs have been fighting for territory.

The battalion was in the news last December when members shot four employees of the town of Arcelia in nearby Guerrero state, including the director and deputy director of municipal transportation, as they drove on a rural road returning from a shooting range. Arcelia is also the hometown of several of those killed in the June shootout. The army said the employees, who were carrying rifles and dressed in hunting camouflage, were mistaken for criminals. A sergeant, a corporal and two soldiers were arrested.

The 102nd was also in the spotlight in February 2012. Citing legal documents, the newspaper Reforma reported that throughout 2010 and into early 2011, soldiers in the battalion took money to inform La Familia of their operations. Six people, including two officers, were charged.

The latest incident was initially reported as a firefight on June 30 in which 22 suspected criminals were killed and one soldier was wounded. The official version came into question when The Associated Press visited the scene days later and found no signs of a prolonged battle.

Last week, a woman who says she witnessed the events told the AP that only one person died in an initial gunbattle and that the rest were shot after surrendering. The witness said the dead included her 15-year-old daughter, Erika Gomez Gonzalez, who had been wounded in the leg and was lying on the ground when she was killed.

The newspaper La Jornada published photos Friday showing bloody bodies, purportedly in the immediate aftermath of the shooting, with investigators and military personnel still at the scene.

The bloodstains on the cinderblock wall, evidence markers and debris shown in the pictures match those that AP journalists photographed days after the deaths were reported by the army.

Among the dead in the photographs is a girl lying on her back in the manner that the witness described. Erika Gomez's brother identified her in the photograph, lying next to an assault rifle, by her bloody and mud-covered clothing.

"I bought her that T-shirt," Saddam Guzman Gomez told the AP. "It's not true that she was shooting. They planted that gun. It looks like she was crawling."

Many of the dead are shown sprawled beside the wall of the warehouse. All pictured are holding or lying near assault rifles, which in some cases appear propped against the bodies. Most have mud on their knees, indicating they may have been kneeling or lying face down.

The AP is not distributing the photographs because it cannot determine their source.

A plain yellow envelope containing the photos on a USB memory stick was sent anonymously on Wednesday to MVT, a local news agency in Mexico state, said the agency's director, Mario Vazquez. He checked the photos with those his agency took the day of the shooting and concluded it was the same scene.

The officer and seven soldiers face disciplinary action for their participation, but the army has remained mum on what roles they played. They were being held at a prison in Mexico City on charges of crimes against military discipline, disobedience and dereliction of duty.

The federal Attorney General's Office is also carrying out a civil investigation, and the governmental National Human Rights Commission is conducting its own probe.

On Friday, Mexico's secretary of the interior defended the armed forces in a meeting in the lower house of Congress.

"If there was something they have done wrong, it would be the exception," Miguel Angel Osorio Chong said of the eight detained soldiers. "It's an isolated incident and doesn't reflect the behavior of our great army and navy in Mexico."

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Associated Press writers E. Eduardo Castillo and Emilio Lugo contributed to this report.