The six guards have been under investigation since a convoy of heavily armed Blackwater contractors opened fire in a crowded Baghdad intersection on Sept. 16, 2007. Witnesses say the shooting was unprovoked, but Blackwater, hired by the State Department to guard U.S. diplomats, says its guards were ambushed by insurgents while responding to a car bombing.
Young children were among the victims and the shooting strained relations between the U.S. and Iraq. Following the shooting, Blackwater became the subject of congressional hearings in Washington and insurgent propaganda videos in Iraq.
An Iraqi government spokesman, Ali al-Dabbagh, said Baghdad welcomed any attempt to "hold the criminals accountable for their crime."
The Iraqi government, he said, has retained a law firm to pursue compensation for the families of the victims.
The Justice Department obtained the indictment late Thursday and got it sealed, according to the people close to the case. The indictment could be made public as early as Monday.
The exact charges in the indictment are unclear, but prosecutors have been considering manslaughter and assault charges against the guards for weeks. The Justice Department has also considered bringing charges under a law, passed as part of a 1988 drug bill, that carries a mandatory 30-year prison sentence for using a machine gun in a crime of violence.
One of the six guards has been negotiating to reduce the charges against him in return for cooperation. If completed, such a deal could provide prosecutors with a key witness against the other five. Others in the convoy have already testified before a federal grand jury about the shooting.
Justice Department spokesman Dean Boyd declined comment.
Blackwater spokeswoman Anne Tyrrell said, "We've consistently said that we do not believe the guards acted unlawfully. If it is determined they did, we would support holding them accountable."