oslo/moscow norwegian rescuers believe may locate sink wreckage russian helicopter go miss thursday eight people aboard coast arctic svalbard archipelago find oil spill air bubble rise surface vessel area observe appear submerge object may helicopter tear hongset leader norway rescue coordination center tell reuters remotely operate mini submarine fly site would likely deploy early hours friday help verify whether discovery make add search survivors would continue rescue center say note helicopter equip life raft russia emergency ministry say five crew three passengers russians russian-made mil mi-8 aircraft report miss around 1335 gmt three passengers work russia arctic antarctic research institute russian energy ministry say statement helicopter way abandon pyramiden settlement coal mine port barentsburg late confirm go ocean kilometers destination several vessels area accord ship data marinetraffic.com ship governor svalbard polarsyssel coordinate search russian coal company arktikugol run coal mine barentsburg employ russian ukrainian miners official russian company convers avia air tell reuters own helicopter lose communication early hongset tell norwegian broadcaster tv2 every minute go risk hypothermia death rise locate around 700 kilometers 435 miles north european mainland svalbard govern treaty grant nato-member norway sovereignty allow signatories business exploit natural resources 40 countries party treaty moscow maintain presence islands decades strategic foothold high north norway say sink russian helicopter wreckage may locate