An investigation by Finnish and Estonian authorities into damaged infrastructure in the Baltic Sea concluded that the damage was most likely caused by human activity – potentially sabotage – eng.lsm.lv, the website of national broadcaster LSM, reported on October 23.

The Finnish police believe that the gas pipeline was damaged not by an explosion, but by a "mechanical" impact.

Suspicion currently falls on ships that lingered nearby at the time the damage was done, especially a Hong Kong-flagged cargo ship that was above the Balticconnector gas pipeline at the time the leak occurred. An subsea cable was also damaged. There were also two Russian ships nearby, reported LTV's De Facto.

One of the lines of investigation is the study of nearby ships. At the time of the event, the Russian ship SVG Flot was anchored nearby. At approximately the moment when the gas pipeline lost pressure, two cargo ships passed above it one after the other: Newnew Polar Bear flying the Hong Kong flag, and Sevmorput, a nuclear-powered ship belonging to the Russian state company Rosatom.

Less than two hours later, on the way to the port of St. Petersburg, the two ships also crossed an underwater telecommunications cable belonging to the Finnish company Elisa, which was also damaged that night. Estonian investigators announced on Thursday that the damage to the cable was caused by human action.

Sweden also reported damage in a similar time frame this week. The Swedish cable to Estonia EE-S 1 lost approximately half of its capacity. The damage was not serious and the cable has now been repaired. The place of damage was located 50 kilometres west of the Estonian island of Hiiumaa.

It is not yet clear whether the incidents are related, though the Swedish cable was also crossed by the ships Newnew Polar Bear and Sevmorput on October 7.

Russia denies that it had anything to do with the damage to infrastructure in the Baltic Sea. The company Rosatom wrote in a statement that its ship cannot be at fault, based on the constant speed of the ship during the crossing of the Balticconnector.

On October 20, the Finnish investigators announced that the focus of the investigation is the Chinese ship that was closest to the Balticconnector when the damage occurred. A heavy object, possibly related to the incident, was also found in the seabed.

In the statements of the Finnish and Estonian authorities, there are no direct accusations of Russian involvement in the damage, however, suspicions remain. Charlie Salonius-Pasternak, a senior researcher at the Finnish Institute of Foreign Affairs, said  that Russia's motive for such action could be to test the reaction of new Nato member state Finland and its allies.

Nato's response was discussed by the alliance's defence ministers during a meeting a week ago. Latvian Defence Minister Andris Spruds (Progressives) said that one of the lines of action is to increase the military presence for the protection of infrastructure. 

On October 19, Nato announced that it will increase patrols in the Baltic Sea, eng.lsm.lv said.