It had announced Sunday that charges were filed against five soldiers after an investigation into allegations that men from the 101st Airborne Division raped and killed the woman, then fatally shot her father, mother and sister at their home in Mahmoudiya, south of Baghdad.
Sgt. Paul E. Cortez, Spc. James P. Barker, Pfc. Jesse V. Spielman and Pfc. Bryan L. Howard are accused of rape and murder and several other charges as alleged participants. They could face the death penalty if convicted.
A fifth, Sgt. Anthony W. Yribe, is charged with failing to report the attack but is not alleged to have been a direct participant.
All five will face an Article 32 hearing, the military equivalent of a grand jury proceeding, to determine if they should stand trial.
They are charged with conspiring with former soldier Steven D. Green, who was arrested in the case last month in North Carolina. Green has pleaded not guilty to one count of rape and four counts of murder. He is being held without bond in Kentucky.
The U.S. military spokesman in Iraq, Maj. Gen. William Caldwell, declined to comment further on details about the attack, saying the investigation is continuing.
"But they obviously had enough information in the initial investigation to go ahead and charge those four soldiers all with alleged rape, rape, obstruction of justice, housebreaking, arson and the other offenses," he told reporters in Baghdad.
According to an FBI affidavit filed in Green's case, he and at least two others targeted the young woman and her family for a week before the attack, which was not revealed until witnesses came forward in late June.
The soldiers drank alcohol, abandoned their checkpoint, changed clothes to avoid detection and headed to the victims' house, about 200 yards from a U.S. checkpoint in the "Triangle of Death," a Sunni Arab area south of Baghdad known for its violence, the affidavit said.
The affidavit estimated the rape victim was about 25. But a doctor at the Mahmoudiya hospital gave her age as 14. He refused to be identified for fear of reprisals.
Green is accused of raping the woman and killing her and the three other family members, including a girl estimated to be 5 years old. An official familiar with the investigation told The Associated Press that Green set fire to the rape victim's body in an apparent cover-up attempt.
Iraqi authorities identified the rape victim as Abeer Qassim Hamza. The other victims were her father, Qassim Hamza; her mother, Fikhriya Taha; and her sister, Hadeel Qassim Hamza.
CBS News correspondent David Martin reports that according to Green's arrest warrant, two of the soldiers have already confessed, saying Green took the girl's parents and younger sister into a bedroom and closed the door. Shots were fired and Green came out, saying, "I just killed them." Green and one other soldier then raped the girl before Green shot her in the head, wrapped her body in a blanked and set it on fire.
Seventeen American soldiers are facing murder charges, reports Martin, and the biggest case — the killing of 24 Iraqi civilians in Haditha — is still under investigation.
U.S. officials are concerned the case will strain relations with Iraq's new government and increase calls for changes in an agreement that exempts American soldiers from prosecution in Iraqi courts.
Prime Minister Nouri al-Maliki has demanded an independent investigation into the case, which comes after a series of allegations that U.S. troops killed and mistreated Iraqi civilians.