The Swedish Security Service said the probe confirmed that "detonations" caused extensive damage to the Nord Stream 1 and Nord Stream 2 pipelines last week.

Sweden’s domestic security agency said Thursday that its preliminary investigation of leaks from two Russian gas pipelines in the Baltic Sea “has strengthened the suspicions of serious sabotage” as the cause.

The Swedish Security Service said the probe confirmed that “detonations” caused extensive damage to the Nord Stream 1 and Nord Stream 2 pipelines last week. Authorities had said when the leaks off Sweden and Denmark first surfaced that explosions were recorded in the area.

The agency didn’t give details about its investigation. But in a separate statement, Swedish prosecutor Mats Ljungqvist said, “Seizures have been made at the crime scene and these will now be investigated.”

Ljungqvist, who led the preliminary investigation, did not identify the seized evidence. Now that the initial probe is completed, a blockade around the pipelines off Sweden will be lifted, he said.

The governments of Denmark and Sweden previously said they suspected that several hundred pounds of explosives were involved in carrying out a deliberate act of sabotage. The leaks from Nord Stream 1 and 2 discharged large amounts of methane into the air.

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