Germany has found traces of explosives in samples taken from a yacht that it suspects "may have been used to transport the explosives" to blow up the Nord Stream 1 and 2 gas pipelines, according to a letter written with Sweden and Denmark updating the UN Security Council on the probe.

The three representatives highlighted to the UN's most powerful body that the investigation was ongoing.

According to Reuters news agency, the three representatives are conducting separate investigations and sent an update ahead of a meeting of the 15-member Security Council called by Russia on Tuesday. Russia has complained about not being informed about the probes. 

In Germany, the investigation has reportedly focused on a chartered sailing yacht. According to German media reports, the yacht left the northeastern port city of Rostock. It was allegedly rented by a company based in Poland that seems to have belonged to two Ukrainians. 

Still no explanation for pipeline explosions

The Nord Stream 1 and 2 gas pipelines were hit by a series of unexplained explosions under the Baltic Sea last September in the exclusive economic zones of Germany, Sweden and Denmark. Shortly after, four leaks were discovered.

Nord Stream 1 supplied a significant share of the gas imported into Europe starting in 2011. Neither pipeline was delivering gas at the time of the attack amid an energy stand-off between the European Union and Russia as a consequence of the Ukraine war.

What else did the letter say? 

"Traces of subsea explosives were found in the samples taken from the boat during the investigation," said the joint letter dated Monday from the UN ambassadors from Germany, Denmark and Sweden to the UN Security Council in New York.

"According to expert assessments, it is possible that trained divers could have attached explosives at the points where damage occurred to the Nord Stream 1 and Nord Stream 2 gas pipelines, which are laid on the seabed at a depth of approx. 70 to 80 metres," it said.

"At this point it is not possible to reliably establish the identity of the perpetrators and their motives, particularly regarding the question of whether the incident was steered by a state or state actor," the letter said.

los/sms (Reuters, dpa)