A Russian Navy ship specializing in submarine operations was present near the sites of the sabotage of the Nord Stream gas pipelines shortly before the explosions in late September. The Danish military confirmed it had 26 photographs of the SS-750 ship, which includes a midget submarine, taken in the Baltic Sea four days before the September 26 explosions.
Responsibility for the submarine attack remains a mystery despite criminal investigations in neighboring countries. The New York Times had said in early March, on the basis of information consulted by US intelligence, that a "pro-Ukrainian group" would be behind the sabotage.