Washington, March 30 : Nine US servicemen of the elite 101st Airborne Division - the US Army's sole air assault formation - were killed when two Black Hawk helicopters crashed during a "routine training mission" in US' Kentucky state late on Wednesday, media reports said. The incident, involving the 101st Airborne Division, happened during a training mission near the Fort Campbell military base at around 10 p.m. local time (2 a.m. GMT) on Wednesday, the BBC reported. It said the US military officials termed the incident as a "truly tragic loss". Crew members were flying "during a routine training mission when the incident occurred", the Fort Campbell base said in a statement on Facebook. Kentucky State Police got the call at around 10.15 p.m. (local time) and rushed to an area with a field and woods, State Police Post 1 spokesperson Trooper Sarah Burgess said, adding that no residential areas are affected. As per the BBC, a US Army spokesperson, in a statement issued earlier, said two HH60 Black Hawk helicopters had crashed during "a routine training mission" and the incident was under investigation and more information would be released as they become available. /IANS