According to the local administrator, Danish police have been looking for a yacht on a small Baltic Sea island close to the explosion sites for the Nord Stream pipeline.

The raid on a ship that may have been used to transfer explosives used to blow up the pipes was confirmed by German authorities on Wednesday.

“The police was searching for a certain yacht that had anchored here in September,” Soren Thiim Andersen, the senior authority on the island of Christiansö, told Reuters.

The Sept. 26 explosions on the Nord Stream pipelines, constructed to supply Russian natural gas to Europe, have become a flashpoint between the West and Russia after last year’s Russian invasion of Ukraine.

Authorities in Sweden, Germany and Denmark, who are currently investigating the blasts, say the explosions were deliberate but have not said who might be responsible.

However, this week media reports in the United States and Germany suggested a pro-Ukrainian group could be responsible.

Germany’s ARD broadcaster and Zeit newspaper reported that German authorities were able to identify a boat used for the sabotage operation.

The operation to place explosives on the seabed was carried out by six people, who sailed from Rostock on Sept. 6 and was later located on the Danish island of Christiansö, according to the reports.

Danish police in January searched for information about boats that had docked on Christiansö on Sept. 16-18, interviewing local residents, collecting footage from the harbour, and collected information from the harbour ticket machine, Andersen said.

Danish police declined to comment.

Christiansö is part of a small archipelago about 18 km northeast of the Baltic Sea island of Bornholm. The archipelago with just 98 inhabitants is a former naval fortress but remains under administration of the Danish defence ministry.