2 military helicopters collide in Kentucky, USA: 9 people killed, accident during training mission

Two military helicopters collided on Wednesday night in Kentucky, USA. According to media reports, 9 people were killed in this accident. Late-night American officials confirmed this.
The accident happened near Fort Campbell Military Base in Trigg County, Kentucky. A military officer told that two HH60 Blackhawk were on routine military training. The governor of Kentucky said this is bad news.
According to a Reuters report, teams of rescuers were deployed from different locations in Kentucky. According to the BBC, the helicopters that collided with each other were from the 101 Airborne Division, the only one attacking America.
These have been deployed during hostilities in many countries of the world. A Fort Campbell spokesman says the incident is under investigation. Five years ago in 2018, two soldiers were killed in a helicopter crash in the Fort Campbell area of Kentucky.
At the same time, according to the report of the New York Times - the weather in the Fort Campbell area was completely clear on the morning of the accident. The wind was also not blowing fast. Visibility was up to 10 miles and the temperature was 39 degrees. In such a situation, how this crash happened, is being investigated.