The explosions that occurred in September at the Nord Stream 1 and 2 gas pipelines in the Baltic Sea resulted from sabotage.
Swedish prosecutor Mats Ljungqvist, who is in charge of the investigation, announced this on Friday.
Explosives residues were found on several foreign objects near the pipelines, it said. However, further research is underway to draw a definitive conclusion.
The explosions caused four gas leaks in the pipelines that normally carry Russian gas to Germany. But the war in Ukraine has turned those gas supplies into a political weapon.
The European Union and NATO, among others, have already assumed sabotage.