Hopes of finding survivors from a Russian helicopter which disappeared off the coast of the Arctic Svalbard archipelago faded on Friday as Norwegian rescuers searched in vain for a second day in ice-cold waters.

Eight Russian men - five crew and three passengers - were listed as missing by Norway’s rescue coordination center, while the location of the Russian-made Mil Mi-8 aircraft remained unknown more than 24 hours after it disappeared.

The helicopter was on its way from the abandoned Pyramiden settlement to the coal mining port of Barentsburg where the Russian coal company Arktikugol runs a mine employing Russian and Ukrainian miners.

“The assumption is that the helicopter has crashed during the approach two kms north of Kapp Heer,” the Accident Investigation Board said in a statement, referring to the local helicopter base.

Snowy weather and high waves were complicating efforts in a region that has almost no daylight at this time of the year, while the air temperature was around minus three degrees Celsius (27 degrees Farenheit).

A search using a small, remotely-operated submarine, yielded no sign of the helicopter, the rescue coordinators said, dashing earlier hopes that a submerged wreckage had been located.

A somewhat bigger submarine will be flown in and is expected to be operational on Saturday, the rescue center said.

“We’re still conducting a search and rescue operation. We’ve not moved to a recovery phase, and won’t do so until the new submarine has completed its search” a spokesman for the Norwegian coordinator said.

Located around 700 kms (435 miles) north of the European mainland, Svalbard is governed under a treaty that grants NATO-member Norway sovereignty while allowing other signatories to do business and exploit natural resources.

More than 40 countries are parties to the treaty. Moscow has maintained a presence on the islands for decades as a strategic foothold in the high north.