Finnish police said on Thursday they are investigating whether a foreign ship was involved in the damage of an undersea power cable connecting Finland and Estonia following a sudden outage on Wednesday.

Finland’s prime minister says authorities are investigating an interruption in a power cable under the Baltic Sea between his country and Estonia.

Finnish authorities said on Saturday they are moving an impounded tanker closer to port after boarding the vessel carrying Russian oil earlier this week on suspicion it had damaged an undersea power line and four telecoms cables.