Finnish police said they had made progress in a criminal investigation into damage caused to an undersea telecommunications cable owned by operator Elisa.
Police seized the cargo vessel "Fitburg" on Wednesday while it was en route from Russia to Israel on suspicion that it had sabotaged the telecoms cable running across the Gulf of Finland from Helsinki to Estonia.
Investigators said they had arrested two of the 14 crew members, imposed a travel ban on two others and had begun questioning them.
The 14 crew members were nationals of Russia, Georgia, Kazakhstan and Azerbaijan.
"The interviews have clarified the course of events and the different roles of the crew members," Detective Chief Superintendent Risto Lohi of Finland's National Bureau of Investigation said in a statement.
The Fitburg, which carried a cargo of steel products, was seen dragging its anchor in the ocean at the time of the incident, and was boarded by Finnish authorities and brought to shore for inspection, investigators have said previously.
Finnish authorities have said the telecommunications cable is currently inoperable but the full extent of the damage will not be known for some time.
Estonian President Alar Karis said the incident was hopefully not a deliberate act, but that the investigation would clarify matters.
The Baltic Sea region, of which the Gulf of Finland is part of, has been hit by a string of incidents in recent years in which gas pipelines, power cables and telecoms links on the seabed were damaged, triggering extensive criminal probes.
Concern is growing in Europe at what officials see as an increase in hybrid threats from Russia since it launched its war in Ukraine, which Moscow denies.
Russia's embassy in Helsinki said it was in contact with Finnish authorities.
"We hope that the situation will be resolved in a spirit of cooperation and in accordance with the relevant legal norms," it said in a statement.
