The Dutch Coast Guard mounted a rescue operation Wednesday in the North Sea, after two cargo ships collided off the southern coast of the Netherlands.

Reports late Wednesday quote Coast Guard officials as saying they believe the cargo ship “Baltic Ace” was sinking some 50 kilometers from the Dutch port of Rotterdam, after colliding with a container ship in heavily-traveled shipping lanes.

A Coast Guard spokesman said crew members from the Bahamas-flagged Baltic Ace were found on four life rafts and that people were being plucked from the sea by helicopters.

The spokesman also said the 12-member crew of the container ship, “Corvus J,” remained aboard the badly damaged ship. but that the Cyprus-flagged vessel was in no immediate danger of sinking.