Finnish investigators probing last week’s disruption to a key telecommunications cable in the Gulf of Finland say they have found clear signs that a ship’s anchor scraped across the seabed for tens of kilometers.

The vessel at the center of the case is the general cargo ship Fitburg, which was seized by Finnish special forces on December 31 after underwater surveys revealed a long trail of anchor drag marks leading directly to the damaged Elisa cable.

“Based on the investigations carried out so far, there is reason to suspect that the Fitburg vessel’s anchor and anchor chain dragged along the seabed at least tens of kilometers before the damage point,” Finnish authorities said in a statement Sunday.

The Central Criminal Police are treating the case as possible sabotage, investigating suspected aggravated damage, attempted aggravated damage, and aggravated interference with telecommunications.

Detective Chief Superintendent Risto Lohi, who is leading the investigation, said authorities are now focused on determining whether the incident was accidental or deliberate.

“The technical and tactical investigation is progressing with the help of several authorities. The focus is on assessing intent and the information that influences it,” Lohi said.

The Fitburg, flying the flag of St. Vincent and the Grenadines, was traveling from Russia to Israel carrying steel products when it was intercepted. Finnish Border Guard helicopters and patrol vessels shadowed the ship before special operations teams rappelled onto the deck and took control in what officials described as a coordinated multi-agency operation.

Underwater surveys are being carried out jointly with Estonian authorities to map the full extent of the seabed damage. On Sunday, the Helsinki District Court ordered the arrest of one crew member, bringing the number of crew under detention or travel restrictions to four.

All 14 crew members — nationals of Russia, Georgia, Kazakhstan, and Azerbaijan — have been questioned since the ship was escorted to the port of Kantvik.

“This case shows that national and international cooperation between authorities works seamlessly,” Lohi said, referencing the joint Finnish-Estonian investigation team.

The incident comes as the Baltic Sea is increasingly viewed as a hotspot for so-called “hybrid threats,” following a string of suspicious breaks to gas pipelines, power links, and telecom cables since Russia’s invasion of Ukraine.

Finnish officials stressed that the damaged cable has not disrupted everyday communications.

“Internet use is not dependent on a single cable,” authorities said, noting that traffic is automatically rerouted through backup systems when faults occur.

For now, the Fitburg remains under guard as forensic analysis of equipment and materials collected on board continues — a process investigators say could take several weeks.