"Additional criminal suspicions have arisen, including gross sea intoxication, the coast guard said in a statement.
"The coast guard is currently taking a number of investigative measures, including various types of coercive measures within the framework of the preliminary investigation."
Two Danish crew members of a capsized barge were missing in the freezing Baltic Sea on Monday after an overnight collision with a vessel in a busy maritime route off Sweden.
Emergency services are also working to bring one of the ships, which capsized, closer to land so that divers can look for the missing persons in the ship's interior.
Footage from the site, not far from the Danish island of Bornholm, showed one of the vessels overturned and lying with its keel up.
The exact cause of the incident is not yet clear.
"We can confirm that two ships collided in the Baltic Sea this morning," a spokesman for the Swedish Maritime Administration, Jonas Franzen, confirmed to DPA.
The vessels involved were the Danish Karin Hoj and the British Scot Carrier.
The Danish freighter is the one that overturned, according to Franzen.
with DPA
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