Few details were immediately available about the crash, which happened near Fort Campbell.

It was not immediately clear whether there were casualties. The spokeswoman, Nondice L. Thurman, said in a statement early Thursday that the status of the crew members was unknown.

Governor Andy Beshear said on Twitter that fatalities were expected, and that the Kentucky State Police and the state’s Division of Emergency Management were responding to the accident.

The two HH60 Black Hawk assault helicopters crashed into each other at about 10 p.m. during a routine training mission, in Trigg County, said Ms. Thurman, who works at Fort Campbell, a sprawling Army base along the Kentucky-Tennessee border.

“The command is currently focused on caring for the service members and their families,” she said, adding that the crash was under investigation.

No other details, such as the number of people aboard the helicopters, were immediately available.

This is a developing story.