There are concerns that Russia's undersea gas pipelines could have been attacked to increase pressure on the West.
Four breaches have now been found in Nord Stream one and two - amid continuing tensions over the war in Ukraine.
Danish Prime Minister Mette Frederiksen believes sabotage is involved:
"Of course it has been very important for me to underline that the Danish authorities have said that this is not an accident. This is something that someone has planned to do in the economic zone in Sweden and Denmark".
