Mexico's Civil Rights Commission says it is investigating the circumstances of a June confrontation between the army and a suspected drug gang that left 22 people dead.

The revelation came Thursday after The Associated Press quoted a woman as saying she saw soldiers fatally shoot her 15-year-old daughter in the incident even though the girl was lying wounded on the ground. Twenty others also were shot to death after they surrendered and were disarmed, the mother said. She said one youth was slain earlier in a gunbattle with the troops.

The Mexican government has maintained that all 22 died during a fierce shootout when soldiers were fired on in the early morning of June 30. That version came into question because government troops suffered only one wounded, and physical evidence at the scene pointed toward more selective killings.

"We have an investigation and are discussing the case to find out what really happened," Human Rights Commission President Raul Plascencia said.

According to the witness, only one gunman died in the initial shootout, and another gang member and her daughter were wounded. The rest of the gunmen surrendered on the promise they would not be hurt, she said, speaking on condition of anonymity for fear of reprisals.

After the gang surrendered, the girl, Erika Gomez Gonzalez, lay face down in the ground, a bullet wound in her leg. Soldiers rolled her over while she was still alive and shot her more than a half dozen times in the chest, her mother said. Another suspected gang member was injured in the initial attack.

"A soldier stood the kid up and killed him," said the witness, who said she had gone to the warehouse the night before to try to retrieve her daughter from the gang she had apparently joined.

The soldiers interrogated the rest of the gang members in front of the warehouse, and then took them inside one-by-one, she said. From where she stood just outside the warehouse and in army custody, she heard gunshots and moans of the dying.

Several days after the killings, AP reporters visited and took pictures of the warehouse and found little evidence of sustained fighting. There were few stray bullet marks and no shell casings. At least five spots along the warehouse's inside walls showed the same pattern: One or two closely placed bullet pocks, surrounded by a mass of spattered blood, giving the appearance that some of those killed had been standing against the wall and shot at about chest level.

After the AP report, the state of Mexico prosecutors' office released a statement 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."

The state government refused to release autopsy reports that the AP requested under Mexico's freedom of information law, declaring them state secrets to be guarded for nine years.

The woman said she is putting herself in danger by speaking out and is in fear of her life. She wants to leave the country. When asked why she decided to speak, she said because of her anger.

"For the truth and because of what the soldiers did. It wasn't right," she said. "According to them they protect us. But no, they're here to kill people."

Interviewed separately, relatives of three other gang members who were killed and a doctor who saw Erika's body said the wounds were consistent with the mother's account of how they were killed — with an incapacitating wound and a burst of gunshots to the chest.

The death certificate for Erika, seen by reporters, confirmed that she died June 30 outside the town of San Pedro Limon, where the killings occurred, and gave bullet wounds as the cause of death. There are no details in the certificate on ballistics or the type of weapon used. The gravestones of two others of those killed, Marcos Salgado Burgos, 20, and his brother, Juan Jose Salgado Burgos, 18, also record their deaths as on June 30.

Separately, a teenager in the nearby town of Ixcapuzalco, said his older brother was among the 22 dead. He said he saw the body and said there was a bullet wound to the left leg — "it destroyed his knee" — and a shot through the back with an exit wound through the chest. His account could not be independently corroborated.

None of the relatives wanted to be identified for fear of reprisals. The army and the state of Mexico so far have not provided a list of those killed. Human Rights Watch has demanded that the case be thoroughly investigated and that the witness be protected.

According to Erika's mother, the shootout was initiated by the army, a violation of its own rules of engagement, which allow soldiers to fire on armed civilians only if the civilians shoot first, and if soldiers' or civilians' lives are in danger. The army did not respond to requests for comment.

The federal Attorney General's Office said there is an open investigation into the incident but no evidence has been found so far to corroborate the witness' account, originally reported by the magazine Esquire Latinoamerica.

The woman spoke angrily last weekend about her daughter's death. She said she spent a sleepless night sitting on a pile of bricks June 29, after arriving to retrieve her runaway daughter.

The girl was involved with the wrong crowd, she said. The group had traveled from the town of Arcelia in Guerrero state to nearby San Pedro Limon in three pickups with guns. All were teenagers or in their early 20s. Little is known about what the gang was up to or had been doing in the days before the shootings.

Local officials said Arcelia is controlled by the La Familia drug gang, which was run out of Michoacan state, where it was founded and now controls parts of the impoverished Tierra Caliente, or hot land, in neighboring Guerrero. Drug trafficking and conflicts with the military have occurred there for decades. Some farmers grow and traffic marijuana and poppies for opium, and violence is common.

Recently, supporters of the gang blocked roads and burned four Coca-Cola trucks, leading the soft drink company to shutter its distribution center in Arcelia. Local journalists say they have been threatened for publishing stories the drug cartel didn't like.

It was unclear if the AP was allowed to report freely in the area because the story casts the army in a poor light. But the gang appeared to keep close tabs on AP reporters while they were in the region. During an interview with the dead girl's mother in a parking lot, a young man appeared, arms propped on the back of a pickup truck, staring fixedly and remaining until the end.

The area is patrolled heavily by army and marine units. When reporters were at a local soccer match interviewing a relative of the two dead brothers, a three-man marine detachment stood nearby. The unit's leader told the journalists, "It's my turn to interview you," and asked them what they were doing and where they were staying. Other marines photographed the journalists and their press ID cards.

Recalling the morning of her daughter's death, the mother said confusion broke out inside the warehouse before dawn when one of the young gunmen appeared, shouting, "They're on us!"

Troops from the army's 22nd Military Zone were on patrol. Soldiers trained a spotlight on the warehouse and opened fire on those inside, she said.

After an initial exchange of gunfire, soldiers called out to those inside, saying their lives would be spared if they surrendered. The young people walked out with their hands on the back of their necks, she said.

The soldiers took her, two other women and two young men who claimed to be kidnap victims to a semi-enclosed room at one side of the entrance to the warehouse.

From there, under soldiers' custody, the woman could only catch glimpses of what was happening inside

"I was afraid to see too much," she said, saying some of the detainees were shot standing, some kneeling.

After a couple of hours, the two men who had claimed to be kidnap victim were separated from the three women, taken off by troops and shot, apparently because the soldiers did not believe their claims, she said.

The army said in its initial press release that soldiers rescued three women who were kidnap victims. The mother says she was one of three women taken by the army to the Mexico state capital, Toluca, and turned over to a state prosecutors' agent. The other two women were promptly arrested and are still in custody.

The mother said she was photographed next to the guns confiscated from the gang and told she would be arrested if she didn't cooperate with authorities and confirm their version of events. She said she did not know the agent's name, but described her as a tall woman with close-cropped hair who was constantly holding a cigarette. She was later taken to the federal attorney general's organized crime unit in Mexico City, and finally released with no charges.