An investigation into claims that US marines may have deliberately killed civilians in Iraq is nearing its end, the Pentagon says.
Relatives say troops went on the rampage
Official accounts from the Iraqi city of Haditha in November said 15 people were killed by a bomb and firefight.
But reports in the US press say as many as 24 people may have died, and that murder charges may be in preparation.
Moves are being made to prepare the public, perhaps for something shocking, says a BBC correspondent in Washington.
A defence department spokesman said he believed the inquiry into Haditha - being carried out by the Naval Criminal Investigative Service - was nearing an end.
But he would not say what investigators had found, and added that he did not expect an announcement on charges in the next few days.
What took place in Haditha on 19 November last year is not clear.
The US military said in statements issued after the incident that 15 Iraqi civilians had been killed by the blast of a roadside bomb, or in a subsequent firefight between US marines and insurgents.
But local Iraqis told a different story.
The criminal investigation has been seeking to establish whether or not the marines killed civilians in cold blood.
A 10-year-old girl told The Times of London this weekend that US soldiers deliberately shot and killed almost her entire family as she lay hiding in the corner.
Iman Hassan described how she heard the dying groans of her grandfather, mother, father, two uncles and a young cousin.
The Los Angeles Times has also reported that investigators have concluded that marines went on the rampage, killing unarmed civilians, including women and children, after a marine was killed by a roadside bomb.
According to this account, up to a dozen marines were involved either in the incident, or covering it up afterwards.
The LA Times says investigators are preparing to call for charges including murder, negligent homicide, dereliction of duty and filing a false report.
The BBC's Adam Brookes in Washington says it certainly seems that public opinion in America is being prepared for the possibility that the investigators' findings will be shocking.
On Thursday, John Warner, chairman the Senate Armed Services Committee, said there were "established facts that incidents of a very serious nature did take place".
The commander of the US marine corps, Gen Michael Hagee, flew to Iraq the same day and said the scenes and experiences faced by marines "can be numbing".
"There is the risk of becoming indifferent to the loss of a human life, as well as bringing dishonour upon ourselves," he said.
Last week John Murtha, a Democrat member of the House of Representatives and a retired marine said US troops in Haditha "overreacted because of the pressure on them.
"They killed innocent civilians in cold blood. And that's what the report is going to tell."