Rescuers are investigating the site of a ship collision in the North Sea off the Dutch coast, where seven crew members are missing after a frigid night at sea.

Officials say it is unlikely they will find survivors. Thirteen crew members from the cargo ship Baltic Ace were rescued by helicopter Wednesday and expected to recover. Four bodies were also recovered.

The Bahamas-flagged carrier, with a crew of 24 and a load of cars headed for Finland, sank after being struck Wednesday by the container ship Corvus J in heavily traveled shipping lanes about 50 kilometers from the Dutch port of Rotterdam.

The Cyprus-flagged Corvus J remained afloat, and Coast Guard officials said it was in no immediate danger of sinking. It was heading for Antwerp, Belgium, when the crash occurred.

The cause of the collision was not immediately established.

The shipping lane where it occurred is one of the busiest in the North Sea and an important sea channel to Rotterdam, Europe's busiest port.