The 55-metre Karin Hoj barge and 90-metre Scot Carrier were sailing in the same direction when they hit each other in the dark at 3.30 a.m. (0230 GMT) in Swedish territorial waters, maritime agencies in Denmark and Sweden said.
A search-and-rescue operation involving at least nine boats and a helicopter near the site off the Danish island of Bornholm was called off by late morning as the overturned Karin Hog was towed away in waters full of wreckage.
The Danish Meteorological Institute said the fog was not dense and such conditions were “not unusual” at this time of year. Sweden’s Coastguard said an investigation was looking into possible “gross negligence” behind the disaster.
With events seeming to have unfolded fast, Denmark’s Joint Operations Centre (JOC) said there was no sign lifeboats or other emergency equipment were used by the Karin Hoj’s two-person crew. Water temperature is about 4-6 Celsius in the area.
“I can confirm an accident has happened but I do not know the circumstances,” Soren Hoj, managing director of Rederiet Hoj which owns the Karin Hoj, told Reuters.
The barge was sailing from Sodertalje in Sweden to Nykobing Falster in southern Denmark.
The other ship, the 90-metre, British-registered Scot Carrier, was functional and its crew were safe.
Danish authorities said the captain has been subjected to an alcohol test as a standard procedure, which would be delivered to Swedish police. The Scot Carrier was sailing from Hargshamn north of Stockholm to Montrose on Scotland’s east coast, according to Refinitiv Eikon data.
Its owner Scotline said it could not comment on details but was assisting local authorities.
The Swedish Maritime Administration (SMA) said the Danish vessel was empty of cargo and it was unclear what if any the British ship was carrying.
The SMA said at around 1000 GMT it had concluded its search for the two missing crew members at the site of the collision and that further efforts would be taken to locate them once the capsized ship had been towed closer to land.
The waters between Sweden and Denmark see large amounts of maritime traffic. Collisions are rare though in 2006 a small Danish vessel sank after a collision with a Swedish vessel, with all the crew rescued alive after bailing overboard.
By Anna Ringstrom and Nikolaj Skydsgaard
(Reporting by Anna Ringstrom, Niklas Pollard and Johan Ahlander in Stockholm, Nikolaj Skydsgaard and Jacob Gronholt-Pedersen in Copenhagen; Writing by Stine Jacobsen; Editing by Andrew Cawthorne)