HELSINKI, Finland (AFP) — Finnish authorities said Thursday they were investigating an oil tanker that sailed from a Russian port over the suspected “sabotage” of a power cable linking Finland and Estonia.

On Christmas Day, the Estlink 2 submarine cable that carries electricity from Finland to Estonia was disconnected from the grid, just over a month after two telecommunications cables were severed in Swedish territorial waters in the Baltic Sea.

Robin Lardot of Finland’s National Bureau of Investigation said a probe for “aggravated sabotage” had been opened into the oil tanker Eagle S, which flies under the flag of the Cook Islands in the South Pacific.

“The assumption at the moment is that it is a shadow fleet vessel and the cargo was unleaded petrol loaded in a Russian port,” said Sami Rakshit, director general of Finnish Customs.

The shadow fleet refers to ships that transport Russian crude and oil products which are embargoed due to Russia’s invasion of Ukraine.

The Eagle S was en route to Port Said in Egypt and still located in the Gulf of Finland, according to the tracking website Marine Traffic.

It was escorted by a Finnish patrol ship toward the coast near Porkkala, around 30 kilometers west of Helsinki.

“We have already boarded the vessel, spoken with the crew and gathered evidence,” Lardot said.