A body has been found and another person is missing after two cargo ships collided in the Baltic Sea off the Swedish coast, causing one to overturn.
Rescue boats and helicopters searched for hours for the missing crew of the capsized Danish boat Karin Hoej.
Prosecutors have begun an inquiry into alleged gross negligence at sea involving the UK-flagged Scot Carrier.
The coastguard is investigating suspected "gross drunkenness at sea" after the incident early on Monday.
Some people are now reportedly in custody.
The Karin Hoej was eventually towed closer to shore, and divers found the body of of one of the two missing crew on board.
A spokesman for the Swedish Maritime Administration (SMA) said earlier that screams had been heard from the water after the collision in the early hours of Monday.
"It is very cold and dark," Jonas Franzen told the BBC. "The water is about 4C (39F) and the air is about 5C (41F)."
The incident occurred in an area of the Baltic Sea between the southern Swedish coastal town of Ystad and the Danish island of Bornholm, he said. Johan Nilsson, in charge of the rescue operation, told Swedish media the hull of the Danish boat had signs of being completely run over.
The head of the Swedish coastguard's preliminary investigation team, Jonatan Tholin, told Swedish radio that several people had been detained. The BBC has approached the owners of the Scot Carrier for comment.
Mr Franzen said a distress call was received at about 03:30 local time (02:30 GMT) on Monday. When a rescue team later approached the area, they reported "hearing screams in the water".
Two helicopters and several boats from Sweden and Denmark helped with the search, but rescue efforts at sea were stopped hours later.
The Inverness-registered Scot Carrier also initially assisted, with teams attempting to right the Danish ship. It was later being towed to a nearby Swedish port.
All those on board the Scot Carrier were said to be safe and well.
The cause of the collision is not yet clear. According to reports, the boats were travelling in foggy conditions with poor visibility.
Prosecutors have opened an investigation into alleged gross negligence at sea, and the coastguard told the BBC there had been "some criminal suspicions as well, including gross sea drunkenness".
Under Swedish law, having a blood alcohol level of 0.02% or more is a criminal offence on the sea as well as on the road, a lower limit than in the UK, where it is 0.05%.
The Karin Hoej was heading to Nykobing Falster in southern Denmark after leaving Sodertalje, near Stockholm, in Sweden on Saturday. It was not carrying any cargo at the time of the incident.
The Scot Carrier was en route to the east coast of Scotland. It is not clear what cargo it was transporting or how many people were on board.
The Scot Carrier is 90m (295ft) long and the Karin Hoej is 55m, according to the maritime website VesselFinder.
