The US military has opened a criminal investigation into the alleged killing of an Iraqi family by US soldiers.
US soldiers are to be given extra training on ethical behaviour
Little official detail has been given, but unnamed officials say the inquiry includes the alleged rape of one of the victims before she was killed.
The investigation began on Saturday and follows an initial military inquiry.
The probe is the latest in a series of inquiries into alleged abuse of Iraqis by US troops.
The US Army's Criminal Investigation Command was asked to look into the incident after a preliminary military inquiry found reason to open a criminal probe, the military said in a statement in Baghdad.
'No stone unturned'
The criminal investigation was ordered a day after two soldiers said they had heard about the incident in the area of Mahmudiya, south of Baghdad, on 12 March, the statement said.
Unnamed officials said that at least two soldiers from the 502nd Infantry Regiment were being investigated to find out if they had been involved in allegedly raping an Iraqi woman, killing her and three other family members - including a small child, and burning her body.
"The investigation just cracked open. We're just beginning to dig into the details," said US military spokesman Major Todd Breasseale.
"We're not going to leave any stone unturned," he said.
Two soldiers from the same regiment were captured, mutilated and killed earlier this month.
Some reports suggested that this event may have spurred the soldiers to come forward with information about the alleged killings.
Some reports said the military were aware of the killings, but had initially blamed them on sectarian violence.
Mahmudiya is a small town in a mixed Sunni and Shia area south of Baghdad, in an area where insurgents operate, sectarian attacks are common and many US soldiers have died in combat in the last two years.
This is the fifth investigation in recent months into allegations of killings of civilians by American forces in Iraq, but the first to allege rape.
Last Thursday, seven marines and a sailor were charged with murder over the death of a disabled Iraqi man in Hamdaniya in April.
Earlier in the week murder charges were filed against four soldiers over the shooting of three male Iraqi prisoners near Tikrit in northern Iraq on 9 May.
Another Pentagon inquiry is looking into an alleged massacre at Haditha last November, in which 24 civilians are thought to have been killed.
Correspondents say the Hamdaniya and Haditha cases have generated a huge amount of unfavourable publicity for the marines and concern within the corps about the conduct of some in Iraq.