AMSTERDAM (AP) — Rescuers gave up hope of finding any more survivors from a cargo ship that sank in the frigid North Sea off the Dutch coast, saying Thursday they are searching for the bodies of six crewmen still missing. That brings the presumed death toll to 11.

Search planes, helicopters and ships resumed the search that was called off in the early hours, but the icy conditions made survival virtually impossible.

“Given the water temperature and the amount of time that’s passed, we don’t have any hope for more survivors,” Peter Westenburg of the Dutch Coast Guard said. Four bodies were found Wednesday, and 13 survivors were rescued. A fifth body was found and retrieved Thursday by a Belgian government helicopter.

The 148-meter (485-foot) Baltic Ace sank after colliding with the 134-meter (440-foot) container ship Corvus J in darkness near busy shipping lanes some 65 kilometers (40 miles) off the coast of the southern Netherlands. The cause of the collision is not known.

The Dutch waterways agency said it has sent two vessels to the spot to help guide traffic and to lay buoys around the area of the sunken wreck. One is using sonar equipment to establish exactly how deep and where it lies on the seabed.

The agency said it is in contact with the ship’s owner about possible salvage operations.

The Baltic Ace, carrying a cargo of cars, sank quickly as its crew of 24 tried to abandon ship.

Dutch police have identified the five victims whose bodies have been found as two Poles, aged 47 and 50; two Filipinos aged 30 and 51; and a 47-year-old Ukrainian.

Four of the survivors were flown to a hospital in Rotterdam and seven to a military hospital in Belgium. All are expected to recover. The location of the other two survivors was unclear.

Janusz Wolosz, an official with Poland’s embassy in The Hague, said that in addition to the two Polish crew members who have been confirmed dead, three are missing and six crew, including the Polish captain, are recovering after being rescued.

“They were all well-qualified for their jobs,” said Mariusz Lenckowski, of the agency that employed the Polish seamen. He said the Baltic Ace was built in the Gdynia shipyard in Poland in 2007.

The Baltic Ace, sailing under a Bahamas flag, was heading from the Belgian port of Zeebrugge to Kotka in Finland, and the Cyprus-registered Corvus J was on its way from Grangemouth in Scotland to Antwerp, Belgium.

Photos of the Corvus J published by the Coast Guard showed serious damage to its prow, but it was not considered in danger of sinking. Its 12-man crew was unharmed and had assisted in the search Wednesday, but on Thursday it began heading toward Antwerp for repairs.

Sandra Groenendal of the Dutch Safety Board said responsibility for investigating the crash lies with the states under whose flags the ships were sailing — the Bahamas and Cyprus — because the collision happened outside Dutch territorial waters. However, she added it was possible those states would seek Dutch assistance.

The safety board later said in a statement it has offered its assistance in the investigation.

The owner of the Baltic Ace, Ray Car Carriers Ltd., and its manager, STAMCO Ship Management Co. Ltd., put out a statement of condolences to the families of the dead and missing crew, and said they will be offered support.

Company representatives were not immediately available to answer questions about the cargo or how much fuel might still be aboard the wrecked vessel.

Netherlands government data shows 260,000 ships cross through Dutch waters annually, mostly foreign ships. Due in part to the nearby location of Rotterdam, Europe’s largest port, it is one of the busiest shipping lanes in the world, yet fewer than 20 accidents happen annually, and few involve fatal injuries.