Two rescue helicopters with paramedics and emergency workers were dispatched to the site, with a total of 140 people involved in the operation. The helicopter was traveling from Vankor to Staryi Urengoi in the Yamalo-Nenets region when it crashed about 45 kilometers (28 miles) northeast of Staryi Urengoi. Poor visibility and strong winds could have been factors of the accident. “The investigation deals with three main versions of the crash of the aircraft: a violation of the rules of operation and flight safety, equipment failure, and adverse weather conditions. None of these is so far regarded as most likely,” the Investigation Committee said in a statement. A day of mourning was announced for the region following the news of the crash. The Mi-8 helicopter is widely used worldwide.