It remains unclear who was behind the sabotage of the Nord Stream pipelines connecting Russia and Germany which spewed gas into the Baltic last year, Sweden's prosecution authority, which is investigating the incident, said on Thursday.
"We are working unconditionally and turning over every stone and leaving nothing to chance," prosecutor Mats Ljungqvist said in a statement.
"Our hope is to be able to confirm who has committed this crime, but it should be noted that it likely will be difficult given the circumstances."