Salvage crews will try to recover a load of 4,813 cars left behind on a huge ship that is listing at a right angle in the northern Pacific Ocean off Alaska.

The 23 crew members of the Cougar Ace were plucked from their vessel Monday night in a rescue co-ordinated by the U.S. Coast Guard and Alaska's Air National Guard.

The Cougar Ace was disabled and listing 90 degrees to its port side off the Alaskan coast on Monday.
(U.S. Coast Guard/Petty Officer Joseph Zemchak/Associated Press)

The sailors, from Singapore, the Philippines and Indonesia, were flown by helicopters to communities in Alaska. One crew member was treated in Anchorage for a broken ankle, but there were no other injuries.

The ship's owners, Tokyo-based Mitsui O.S.K. Lines, wouldn't confirm what type of cars were on board the 199-metre ship, which was travelling from Singapore to Vancouver.

The Cougar Ace sent out a mayday on Sunday when the ship started to take on water and list sideways about 370 kilometres south of Alaska's Aleutian island chain.

The crew members put on survival suits and gathered in a part of the ship that was still above water to await rescue.

When rescuers reached the vessel, it was floating on its side in the frigid water and appeared poised to sink.

Waves whipping ship

The rescue was conducted late Monday in "very challenging weather," said Master Sgt. Sal Provenzano, with the Alaska Rescue Coordination Center. Three-metre seas were whipping the ship.

Earlier Monday, a coast guard plane dropped three life rafts, but roiling waters shoved the rafts underneath the dipping port side of the ship. Racing against an increasingly tilting ship, rescuers tossed an additional raft along the higher starboard side, but it was a 46-metre drop to the water and beyond their reach.

Communications between the crew and coast guard became increasingly difficult when the batteries in the crew's hand-held radio dimmed, Coast Guard Lt. Mara Booth-Miller said.

Crew members had to shout information to a merchant ship that had rushed to the area after receiving the mayday. That ship relayed messages back and forth to the coast guard.

Eventually all crew members were taken off by helicopter.

Near the vessel, rescuers could see a 3.2-kilometre oil sheen, though officials said it was difficult to say how much of the ship's 430 tonnes of fuel oil or 112 tonnes of diesel fuel had spilled.

With files from the Associated Press