A major electricity interconnector unexpectedly went offline on Christmas day, with officials saying they are not ruling out sabotage, and police are investigating.

Speculation surrounds two cargo ships that passed over the Estlink-2 power interconnector within moments of it going out of service at lunchtime Christmas Day. The subsea power cable, which links the power grids of Russia-neighbors Estonia and Finland can carry 650MW of power and at the time of the outage was exporting at full capacity from Finland.

There were no power cuts in either country, however, as there was surplus power available at the time of the outage.

Finnish authorities have not revealed if the cause of the break in transmission has been positively confirmed, but the cable is still out of action more than a day later. Prime Minister Petteri Orpo said on Wednesday repairs would commence “as soon as the fault location has been identified”.

National police are investigating with the border patrol. It is stated Finnish Police are working on a hypothesis of intentional damage, and a press conference on their findings so far is expected this afternoon.

Finnish broadcaster Yle cites the head of national power grid Arto Pahkin who told the network there were two foreign vessels transiting over the cable at the time of the outage and that “the possibility of terrorism or vandalism cannot be ruled out.”

While sabotage is evidently suspected, it is also possible the outage was the result of a fault. The decade-old Estlink 2 cable, for instance was out of commission between January and August this year due to a fault in a “challenging area”. Estlink-1 has also had fault outages.

Nevertheless, attention has honed in on the two ships, oil tanker Eagle S and Hong Kong-flagged container ship Xin Xin Tian 2. Yle focusses particularly on Eagle S, asserting it transited over the cable just as the power outage was reported, and noting open-source marine tracking indicates the ship suddenly slowed down at this time.

The implication in these reports appears to be the Eagle S may have dropped its anchor deliberately to dredge the sea floor, cutting through any cables it passed. This tactic is alleged to have been used in known cases of sabotage of European underwater infrastructure by Russian-linked ships recently.

Also relevant may be the designation of Eagle by Lloyd’s of London as a member of Russia’s ‘dark fleet’ of obscurely-owned ships engaged in “deceptive shipping practices” to sidestep the Western sanctions regime against Russian oil exports. The ship was intercepted and escorted by a Finnish coast guard vessel [pictured, top] on Christmas Day after the power outage.

Undersea sabotage is becoming a more familiar event for Europe, with governments accusing Russia of waging an undeclared ‘hybrid’ war against the European Union in opposition to the West for having interfered in what it clearly considers a private matter in Ukraine. In November, a Chinese ship the Yi Peng 3 was accused of having cut two telecom cables by dragging its anchor in Swedish territorial waters in the Black Sea.

A joint declaration by Germany, France, Poland, Italy, Spain and the United Kingdom said of the cable cutting then: “Russia is systematically attacking European security architecture… unprecedented in their variety and scale, creating significant security risks”. Attempts at investigating the ship were blocked by Chinese authorities, Sweden said, and the Yi Peng 3 eventually left the area without ever having been boarded by Western officials.