(Fort Campbell) A collision late Wednesday night between two U.S. military helicopters resulted in multiple casualties, military officials said.

The accident happened around 10 p.m. local time in southwestern Kentucky during routine training. Two HH-60 Black Hawk helicopters from the famed 101st Airborne Division were involved.

The 101st Division said the accident caused “several victims”, without specifying whether they were injured or dead. The crash happened in Trigg County, about 30 miles northwest of the town of Fort Campbell.

Kentucky Gov. Andy Beshear previously warned that casualties were expected.

Fort Campbell is near the Tennessee border, about 100 miles northwest of Nashville.

A witness told the local press that he saw two helicopters flying very close to each other before the accident. A gigantic explosion occurred about a minute later.