COPENHAGEN, Denmark (AP) — A Swedish prosecutor wants “a supplementary crime scene investigation" at the site of explosions that damaged two natural gas pipelines in the Baltic Sea and said Friday that a preliminary probe concluded the cause was “suspected gross sabotage."

Prosecutor Mats Ljungqvist said he understood the intense interest in determining what happened to the Nord Stream I and 2 pipelines, which were built to carry Russian gas to Germany.

“But it is important both for the preliminary investigation and for the various collaborations we have that we now get to work in peace and quiet,” Ljungqvist said.

Sweden’s domestic security agency and armed forces are assisting in the investigation, which is being done in cooperation with authorities in other countries," he said.

The Swedish Security Service previously said that undersea “detonations” on Sept. 26 caused extensive damage to the pipelines in international waters off Sweden and Denmark. The pipelines ruptured, sending large amounts of methane gas into the air.

The Swedish navy said on Twitter that it was using minesweepers to perform “supplementary bottom surveys” that were not part of the criminal investigation. It didn’t elaborate on the nature of the work.

Investigators in Sweden, Denmark and Germany are looking into what happened. Danish and Swedish officials have said they suspected several hundred pounds of explosives were involved in carrying out a deliberate act of sabotage.

Nord Stream 1 carried gas to Germany until Russia 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.

Russian President Vladimir Putin accused the West of attacking the pipelines, which Western nations denied.

Ljungqvist, who led Sweden's preliminary investigation, said earlier this month that “seizures have been made at the crime scene" but gave no details.