Swedish investigators confirmed on Friday that the blasts that destroyed sections of the Nord Stream pipelines in September were sabotage, intended to damage the lines carrying natural gas from Russia to Germany under the Baltic Sea.
Investigators found traces of explosives on several foreign objects at the sites of the blasts near Sweden and Denmark, Stockholm prosecutor Mats Ljungqvist said in a statement.
Ljungqvist, who is leading the preliminary investigation, added that technical analyses were continuing in order to "draw more reliable conclusions regarding the incident".
Sweden's Prosecution Authority said that the "continued investigation will show if anyone can be formally suspected of a crime".
Four major leaks were discovered along Nord Stream's two pipelines off the Danish island of Bornholm at the end of September, with seismic institutes recording two underwater explosions just prior to the damage.
Investigators had already said that preliminary inspections had reinforced suspicions of sabotage.
Pipelines under geopolitical pressure
At the end of October, Nord Stream sent a Russian-flagged civilian vessel to inspect the damage.
The pipelines, which connect Russia to Germany, have been at the centre of geopolitical tensions as Russia cut gas supplies to Europe in the wake of EU sanctions on Moscow for the Russian invasion of Ukraine.
Russia has accused the UK of being involved in the explosions, a claim dismissed as "false on an epic scale" by the authorities in London.
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The pipelines were not in operation when the leaks occurred. The gas seen rising to the surface of the Baltic after the explosions was static residual content, left in the system after gas transfer was halted.
Washington and Moscow have both denied any involvement in sabotage.