The Mount Kebnekaise area where the metal objects were detected was designated an accident zone on Friday evening.

Swedish rescue workers leading the search operation in the far north of Sweden said the airplane itself had not yet been found.

“We have now managed to confirm that a Swedish unit at Storglaciären (‘The Grand Glacier’) has found a number of objects,” said the Swedish rescue services.

“They have found a padded object and a Velcro strip, all drenched in paraffin. Photographs have been taken and sent to the Norwegian army.”

Earlier on Friday afternoon, a Norwegian Orion search plane observed an unidentifiable orange-coloured object on a hillside by Mount Kebnekaise.

“The pilots who spotted it were lucky; there must have been a window in the cloud coverage. We sent a Swedish military helicopter up there just after but he saw nothing,” Peter Lindquist of the Swedish sea and air rescue services told the TT news agency.

Problematic weather conditions, with strong winds and blizzards, have hampered the rescue mission for helicopters and ground-based personnel.

According to Per-Olov Wikberg, coordinator for the Mountain Safety Council of Sweden (Fjällsäkerhetsrådet), it is difficult to rate the chances of survival in the type of harsh terrain where the plane is thought to have crashed.

“If you are uninjured, dressed correctly and have access to water, you might manage ten days,” he told TT.

”This is the most alpine terrain we have in Sweden. It is the very worst place to end up in this weather,” he said.

The plane was carrying five Norwegian crew members when it lost radio and radar contact around 2.40pm on Thursday afternoon.

The aircraft went missing when it was on its way from Evenes in northern Norway to Kiruna in the far north of Sweden.

At the time, the Hercules was was participating in the Cold Response military training exercise taking place over northern Norway which was scheduled to run from March 12th to March 21st and included 16,000 soldiers from 15 countries.

"There was a crew of four on board as well as an extra officer. Their mission was to fly from Evenes to Kiruna to pick up materiel and personnel and fly back to Norway," Harald Sunde, head of the Norwegian Armed Forces told Norwegian news agency NTB.

He added that the officers on board the Hercules aircraft were among the "most experienced" in the Norwegian military and that there were no clues regarding what may have happened.

"We have nothing that points us in any particular direction. This is a very robust and new aircraft, one of the best there is. It's been hard to have bad luck with this type of aircraft," said Sunde.

The missing aircraft is a C-130 J "Super" Hercules transport plane manufactured by Lockheed Martin in the United States.

The plane is one of four C-130 Js ordered by the Norwegian air force in 2007, the first of which was delivered in November 2008.