Nine US troops have been killed after a military helicopter crashed in Iraq.
Their Black Hawk helicopter, which was on a medical mission, came down near Falluja, west of Baghdad, but no-one knows what caused the incident.
There have been several attacks on US forces in the area. One US soldier was killed and 34 injured in a mortar attack on Wednesday.
Meanwhile, the US released some Iraqi prisoners, to try to improve relationships between the countries.