Story highlights

The Baltic Ace and its crew of 24 began sinking immediately after the collision

13 people have been rescued; the rescue operation is continuing

(CNN) —  

Rescue operations were under way in the North Sea after a container vessel collided Wednesday night with a car carrier, which had 24 people aboard when it started sinking, a spokesman for the Netherlands Coast Guard said Thursday.

The carrier Baltic Ace began sinking immediately after it collided with the container vessel in a busy shipping lane, about 60 kilometers (32 miles) west of Rotterdam, according to Coast Guard spokesman Peter Verburg.

Thirteen crew members were rescued and taken to hospitals in Rotterdam and at the Koksijde Air Base near Ostend, Belgium.

Those rescued were suffering from hypothermia and minor injuries, the spokesman said.

The nationality of the crew was not immediately known.

Various fishing boats, merchant vessels and at least three helicopters were searching for more survivors.

The Baltic Ace had been en route from Zeebrugge, Belgium, to Kotka, Finland; the container vessel was en route from Grangemouth, Britain, to Antwerp, Belgium.