The Norwegian seismological institute (NORSAR) said it detected "a probable explosion" on October 8 in the Baltic Sea between Finland and Estonia where a gas pipeline leak was later detected.
The statement from the independent institute on October 10 came after Finnish authorities said the subsea gas pipeline and a telecommunications cable connecting Finland and Estonia have both sustained damage, which appears to have been caused by “external activity.”
“The damage to the underwater infrastructure has been taken seriously and the causes have been under investigation since October 8,” President Sauli Niinisto said in a statement.
“It is likely that the damage to both the gas pipeline and the telecommunications cable is the result of external activity,” he added without giving more details.
The NORSAR statement said its stations in Finland "detected a probable blast along the Finnish coast of the Baltic Sea" at 1:20 a.m. local time on October 8.
"The local magnitude of the event has been estimated at 1.0, which is much lower than the Nord Stream explosion detected in September 2022," the statement said. "Both location and magnitude estimates are associated with large uncertainties. Further analysis of the data is ongoing."
The statement referred to a series of blasts in September 2022 that ruptured three of the four pipelines that make up Nord Stream 1 and Nord Stream 2, major conduits for Russian natural gas exports to Western Europe. Denmark, Sweden, and Germany opened probes into the incident, which was deemed to be sabotage, but the case remains unsolved.
Finnish and Estonian gas system operators said on October 8 that they noticed an unusual drop in pressure in the Balticconnector pipeline, after which they shut down the gas flow.
Finnish authorities said on October 10 that they had identified the location of the outage in the 77-kilometer pipeline.
Niinisto said the cause of the damage was not yet clear and the investigation by Finland and Estonia was continuing. Estonia’s Navy told the Associated Press that it was conducting an investigation on the pipeline together with the Finnish military.
NATO Secretary-General Jens Stoltenberg wrote on X, formerly known as Twitter, that he had spoken with Niinisto “on damage to undersea infrastructure.” He said NATO was sharing information and “stands ready to support Allies concerned.”
Both Finland and Estonia are NATO member states, and the pipeline incident is likely to be put on the agenda of a NATO defense ministers’ meeting in Brussels this week.
The Balticconnector pipeline runs across the Gulf of Finland from the Finnish town of Inkoo to the Estonian port of Paldiski. It is bi-directional, transferring natural gas between Finland and Estonia depending on demand and supply.
Commissioned in 2019, the Balticconnector has been the only gas import channel to Finland apart from liquefied natural gas (LNG) since Russian imports were halted in May 2022 following Moscow's invasion of Ukraine.
Russia stopped supplying gas after Finland refused to pay in rubles, a condition imposed on “unfriendly countries” -- including European Union member states -- as a way to sidestep Western financial sanctions against Russia's central bank.
Most of the gas that was flowing in the Balticconnector pipeline before it was closed on October 8 was going from Finland to Estonia from which it was forwarded to Latvia, Estonia’s gas system operator Elering said.
Estonian consumers have been receiving gas from Latvia since the shutdown of the pipeline, Elering said.
Finnish gas operator Gasgrid said the Finnish gas system is stable and the supply of gas has been secured through a floating LNG terminal at Inkoo.