Swedish investigators found traces of explosives at the Baltic Sea site where two natural pipelines were damaged in an act of “gross sabotage”, the prosecutor leading Sweden’s preliminary investigation said.
Mats Ljungqvist of the Swedish Prosecution Authority said investigators carefully documented the area where the Nord Stream 1 and 2 pipelines ruptured in September.
The parallel undersea pipelines run from Russia to Germany.
“Analysis carried out shows traces of explosives on several of the foreign objects that were found” at the site, Mr Ljungqvist said in a statement on Friday.
The prosecution authority said the preliminary investigation was “very complex and comprehensive” and further scrutiny would show whether anyone could be charged “with suspicion of crime”.
Investigators in Sweden, Denmark and Germany are looking into what happened.
Danish officials confirmed in October there was extensive damage to the pipelines caused by “powerful explosions”.
The leaks occurred in international waters but within the exclusive economic zones of Denmark and Sweden.
Investigators have not given indications of who they think may be responsible but reported earlier that the blasts were likely to have involved several hundred pounds of explosives.
Kremlin spokesman Dmitry Peskov said on Friday it is “very important to find those who are behind the explosion”.
Sweden’s findings of “a sabotage act or a terrorist act – you can call it whatever you like” confirm “the information that the Russian side has had”, Mr Peskov said. Moscow needs to wait for a full damage assessment to decide whether to repair the pipelines, he added.
Nord Stream 1 carried Russian gas to Germany until Moscow cut off supplies at the end of August.
Nord Stream 2 never entered service as Germany suspended its certification process shortly before Russia invaded Ukraine in February.