Eighteen people are thought to have died in the accident

Three of the Rocknes's 30 crew members were found dead after the ship tipped onto its side on Monday evening.

Focus has shifted to an investigation aiming to find out what caused the freighter to overturn in calm weather.

Twelve of the vessel's crew members were saved, including three found when rescuers cut a hole through its hull.

After the ship had been towed to shallower water, rescuers heard the three shouting and pounding on the inside.

They were able to free the crew members at 2320 local time (2220 GMT) on Monday, some seven hours after the freighter capsized.

The Philippines' men at sea

But there have been no further signs of life from inside the overturned vessel.

Rescue leader Trygve Sveen told the Associated Press: "The rescue is called off. There is no hope of finding survivors in the water."

And he said it was doubtful that any survivors would now be found inside the ship.

Most of the crew members were Filipinos, with three Dutchmen, two Norwegians and one German also reportedly among them.

Race against time

The 166-metre (550 feet) long freighter sent out a distress call before it capsized about 200 metres from the western island of Bjoroey at about 1630 on Monday (1530GMT).

MV ROCKNES Built: 2001 Crew: 24 Filipinos, 3 Dutchmen, 2 Norwegians, 1 German Length: 166 metres Role: Bulk carrier, carrying rocks for use in construction of underwater pipelines and cables off Germany

Witnesses, some watching in horror from their own homes overlooking the fjord, said it took only seconds.

One former Norwegian pilot of the Rocknes and her sister ship told reporters the ships had been hard to turn in the strong current of the fjord, but he conceded it was difficult to see how that alone could have led to the capsize.

One side of the Rocknes appeared to have been torn open and investigators will try to establish whether she hit the seabed before keeling over

Some crew members were thrown into the icy waters, but were saved because the accident happened close to land and local boats were able to join in the rescue.

Experts had previously put survival times in the dock's icy waters at about three hours.

The MS Rocknes is a bulk carrier that had been loaded with heavy rocks bound for Emden in northern Germany, after loading in the Norwegian port of Eikefet.