The US military announced on Thursday that 9 of its soldiers were killed when two helicopters crashed after colliding during a training mission over Kentucky.
The collision between two Black Hawk helicopters occurred at ten o'clock on Wednesday evening EST (two in the morning on Thursday GMT) in Trig County on the border between Kentucky and Tennessee.
Kentucky State Police said the incident occurred in a field about 50 kilometers from Fort Campbell military base.
Army Secretary Christine Formouth described the incident in which the nine soldiers were killed as a difficult day for the U.S. military.
Army spokeswoman Nondis Thurman said the cause of the incident was still under investigation.
Last month, two U.S. National Guard pilots were killed when their Black Hawk helicopters collided during a training mission in Alabama.