Electricity transmission between Finland and Estonia through the Estlink 2 connection was cut on Christmas Day, according to Finnish grid operator Fingrid.
In a statement, Fingrid said that the cause of the fault is under investigation.
"The possibility of sabotage cannot be ruled out. However, we are examining the situation as a whole and will provide further information once the cause is identified," said Arto Pahkin, Fingrid's Operations Manager.
The transmission line experienced an outage on Wednesday, Christmas Day, at 12:26pm. At the time, the power transfer from Finland to Estonia was 658 megawatts, Fingrid reported.
Finnish Prime Minister Petteri Orpo (NCP) addressed the issue on the social media platform X, stating that the disruption does not affect electricity supply in Finland.
"Authorities remain vigilant, even during Christmas, and are investigating the matter," Orpo wrote.
Jukka Relander, Communications Manager at the industry interest group Finnish Energy, said that the failure of Estlink 2 will not affect the price of electricity on Thursday, at least not significantly.
"Sometimes there are rare occasions when electricity comes to us from Estonia, but more often it's an export cable," Relander explained.
Challenging investigation underway
According to Pahkin, determining the cause of the outage is proving to be a complex task.
"Some of the team have been dispatched to the substation, while others are examining the area between the substation and the sea, as well as the subsea cable itself. Both the Finnish and Estonian ends are being inspected," Pahkin said.
Tabloid Ilta-Sanomat was the first to report the incident in Finland.
Finland and Estonia jointly own the Estlink 1 and Estlink 2 connections. While Estlink 2 remains out of service, Estlink 1 continues to function normally.
"Estlink 2 is an important link, as are all cross-border connections. To ensure the European electricity system operates effectively, it is crucial that all connections remain in use," Pahkin emphasised.
Earlier this year, Estlink 2 underwent several months of maintenance-related closure.
The subsea cable has a transmission capacity of 650 megawatts (MW), while Estlink 1 has a capacity of 350 MW, according to Estonia's ERR news outlet.