Crew feared dead in US helicopter crash in Helmand Province A statement from the Nato coalition headquarters in Kabul did not give details of casualties, or survivors, and said the crash site had been secured. The cause of the incident was under investigation, it said. Crashes occur regularly and the most deadly single incidents for coalition troops have all involved the aircraft either being shot down, or having accidents. Last month 12 Turkish soldiers and two civilians were killed in a crash on the outskirts of the Afghan capital Kabul. In January, six US troops were killed in a CH-53 Sea Stallion helicopter crash in the Musa Qala district of Helmand province. The single deadliest incident for coalition forces during the campaign came in August 2011, when Taliban insurgents shot down a Chinook helicopter in Wardak province, killing 30 Americans and eight Afghans.