In the most recent incidence of possible sabotage to undersea infrastructure, Finland is investigating an oil tanker — believed to be part of Russia’s so-called “shadow fleet” that transports embargoed oil — in the disconnection of an undersea power cable.

The probe comes after multiple other disruptions of telecommunications cables, possibly involving Russia, and explosions at a huge gas pipeline in the Baltic Sea two years ago.

Estonia’s foreign minister, Margus Tsahkna, called the damage to Estlink 2 cable that provides electricity to his country the result of “attacks against our vital structures.”

He said they have become “so frequent” that it appears unlikely they are “accidental” or “merely poor seamanship.”

“We must understand that damage to submarine infrastructure has become more systematic and thus must be regarded as attacks against our vital structures,” Mr. Tsahkna said in a press release. “In addition to circumventing sanctions, the shadow fleet is a security threat in the Baltic Sea, and we cannot just sit and watch.”

The Estlink 2 cable was disconnected from the power grid on Christmas day. 

Finland’s prime minister, Petteri Orpo, shared in a post on X that authorities were investigating the incident but said the “interruption of the transmission connection will not affect the electricity supply of Finns.” The head of Finland’s electricity grid, Arto Pahkin, told the public broadcaster Yle that officials were investigating the possibility the disconnection was the result of sabotage.

A Finnish Coast Guard official told reporters during a press conference that investigators are looking into the Eagle S, which is registered in the Cook Islands. Finnish border guard officials boarded the ship and escorted it to waters on the Gulf of Finland, where it has been anchored. Officials said the Eagle S’s anchor was not in place, which contributed to suspicions that the ship was involved in disconnecting the Estlink 2 cable. The ship tracking website MarineTraffic shows the Eagle S significantly decreased its speed when it passed over the cable. 

The Eagle S was headed to Egypt after it left St. Petersburg. While it was flying the Cook Islands flag, it is believed to be part of Russia’s so-called “shadow fleet.” The director general of Finnish Customs, Sami Rakshit, told reporters, “The assumption at the moment is that it is a shadow fleet vessel, and the cargo was unleaded petrol loaded in a Russian port.”

The British publication Lloyd’s List defines the term “shadow fleet” as ships that tend to be more than 15 years old, typically in poor repair,  and whose actual owner is not known. It is believed that these ships are used to help Russia skirt sanctions on its oil products. 

According to Lloyd’s List, the Eagle S is owned by Caravella, a shipping company based in the United Arab Emirates. Representatives for Caravella did not respond to a request from The New York Sun for comment by the time of publication.

The interruption of the Estlink 2 follows disruptions of telecommunications cables in the Baltic Sea. In November, two telecommunications cables linking Denmark and Sweden were severed. Investigators believed a Chinese ship, the Yi Peng 3, which sailed over the cables when they were cut, was responsible.

The Wall Street Journal reports that the vessel is believed to have dragged its anchor along the seabed for roughly 100 miles as it cut the cables. The ship’s owner was cooperating with investigators, but the company declined to comment on the Journal’s report. 

Swedish officials said on Monday that Communist China rejected requests to let prosecutors investigate the ship and that the vessel had left the area. 

While the ship was owned by a Chinese company, investigators were probing whether Russian intelligence operatives were behind the incident. In a statement to the Journal, the Kremlin press office said the allegations were “absurd” and “unsubstantiated.”

Besides severing cables, there have been other forms of damage to infrastructure in the Baltic Sea, such as the 2022 explosion of the Nord Stream gas pipelines.

Officials expect the repairs on the Estlink 2 cable to take months to complete.