Nine US servicemen have been killed after two army Black Hawk helicopters crashed in Kentucky during a training mission, officials have said.
The incident happened at around 10pm (3am Irish time) in Kentucky's Trigg county, northwest of Fort Campbell, the army base said in a statement.
The US military said it was not clear what happened to the two helicopters.
Brigadier General John Lubas, Deputy Commanding Officer for Operations at the 101st Airborne Division, said it was not clear if the two helicopters had crashed into each other.
He added that one helicopter had five soldiers while the other one had four.
Kentucky Governor Andy Beshear said earlier that fatalities were to be expected.
"We've got some tough news out of Fort Campbell, with early reports of a helicopter crash, and fatalities are expected," Mr Beshear said in a post on Twitter.
Crew members were flying two HH-60 Black Hawk helicopters, operated by the 101st Airborne Division.
The HH-60 is a variant of the Black Hawk helicopter designed to provide support for various military operations, including air assaults and medical evacuations, according to the army.
Fort Campbell is home to the 101st Airborne Division, the US Army's only air assault division.
Nicknamed the 'Screaming Eagles,' the division was activated in August 1942 and gained renown during World War II in the D-Day landings and the Battle of the Bulge.
More recently the division has seen action in Iraq and Afghanistan.
