Sudden and unexplained gas leaks detected in the Nord Stream 1 and 2 pipelines from Russia to Germany have prompted investigations by European countries into the cause amid fear of possible sabotage.

Denmark’s armed forces on Tuesday released video showing bubbles rushing to the surface of the Baltic Sea above the pipelines, and said the largest gas leak had caused surface disturbances of well over one kilometre in diameter.

An energy standoff over Russia’s war in Ukraine halted flows through Nord Stream 1 and prevented the onset of flows through the parallel Nord Stream 2.

Plunging Russian gas supplies have caused prices to soar in Europe, where countries have struggled to find alternative supplies of energy used to heat homes, generate electricity and run factories.

The leaks overshadow the inauguration of the long-awaited Baltic pipeline that will bring Norwegian gas to Poland in efforts to bolster Europe’s energy independence from Moscow.

Here is a breakdown of what is known so far: 

The operator of the Nord Stream 2 gas pipeline reported a sudden drop in pressure overnight on Monday, with a spokesperson suggesting there could have been a leak.

This was followed by a Danish Energy Authority statement that a leak had likely occurred in one of the two Nord Stream 2 pipelines lying in Danish waters.

A few hours later, Nord Stream AG, operator of another undersea gas pipeline from Russia to Germany, said it was looking into a drop in pressure in Nord Stream 1.

Sweden’s Maritime Administration said on Tuesday that it had warned of two leaks on Nord Stream 1 in Swedish and Danish waters.

Anders Puck Nielsen, a researcher with the Center for Maritime Operations at the Royal Danish Defence College, said the timing of the leaks was “conspicuous” given the ceremony for the Baltic Pipe, a new system that will bring Norway’s gas to Poland.

He said perhaps someone sought “to send a signal that something could happen to the Norwegian gas”.

“But I think if we look at who would actually benefit from disturbances, more chaos on the gas market in Europe, I think there’s basically only one actor right now that actually benefits from more uncertainty, and that is Russia,” Puck Nielsen said.

Where are the leaks?

Two leaks were detected on the Nord Stream 1 pipeline, which stopped delivering gas to Europe last month, both in an area northeast of the Danish island of Bornholm.

Danish authorities have asked ships to stay clear of Bornholm by a five nautical mile radius after the leak in Nord Stream 2, which has yet to enter commercial operations. The plan to use it to supply gas was scrapped by Germany days before Russia sent troops into Ukraine in February.

Both pipelines still contain gas under pressure, but are not delivering the fuel to Europe.

Each line of the pipeline consists of about 100,000 24-tonne concrete-weight coated steel pipes laid on the seabed. The pipelines have a constant internal diameter of 1.153m, according to Nord Stream.

Sections lie at a depth of around 80-110m.

What caused the leaks?

It is not yet clear. Analysts and experts say such leaks are very rare, and Nord Stream AG has called leaks on three strings of the offshore gas pipelines “unprecedented”.

Possible causes range from technical malfunctions to a lack of maintenance, to even possibly sabotage.

The Swedish National Seismic Network recorded two “massive releases of energy” shortly prior to, and near the location of, the gas leaks, Peter Schmidt, an Uppsala University seismologist, told AFP.

Ukraine said the leaks were likely the result of a “terrorist attack” carried out by Moscow.

“The large-scale ‘gas leak’ from Nord Stream 1 is nothing more than a terrorist attack planned by Russia and an act of aggression towards the EU,” Kyiv’s Presidential advisor Mikhaylo Podolyak said on Twitter.

The Kremlin has said it did not rule out sabotage as a reason behind the damage, adding it was an issue affecting the energy security of the “entire continent”.

Poland’s prime minister said the leaks were an act of sabotage, while Denmark’s leader said it could not be ruled out.

The European Commission said it was premature to speculate.

German Geology Research Centre GFZ said on Tuesday that a seismograph on Bornholm showed spikes at 00:03 GMT and 17:00 GMT on Monday, when the pressure losses occurred.

Kathryn Porter, an energy consultant at Watt-Logic, a United Kingdom-based independent energy consultancy, said it was extremely “rare” for such a series of leaks to occur within the same general area.

“This is pretty unprecedented,” Porter told Al Jazeera. “Everyone is scratching their heads to try and understand what has happened here and what the motivation behind it could be.

“For pipes to fail, normally you either have something like corrosion or fatigue, but Nord Stream 2 is a brand new pipe. And you could look at maybe some sort of construction problem, such as faulty welding, but on the other hand, there are now issues with Nord Stream 1 and that’s been operating since 2012.

“So it is very difficult to come up with a rational explanation for these things.”

Who is investigating?

For the Nord Stream 2 leak, the head of Denmark’s Energy Agency, Kristoffer Bottzauw, told Reuters it was too early to say who would conduct the investigations. Bottzauw added that no one has been to look at the pipeline yet.

The Swedish Armed Forces, the Coast Guard, the Swedish Maritime Administration and other relevant authorities are taking necessary measures, Swedish Prime Minister Magdalena Andersson said.

Germany on Monday said it was coordinating a response with police, local officials and the energy agency.

Potential impact?

The extent of the damage means the Nord Stream pipelines are unlikely to be able to carry any gas to Europe this winter even if there was political will to bring them online, analysts at the Eurasia Group said.

“Depending on the scale of the damage, the leaks could even mean a permanent closure of both lines,” analysts Henning Gloystein and Jason Bush wrote.

“Leaks of this size are a severe safety and environmental hazard, especially should Russia not stop pumping gas into the system,” the analysts said.

Gas leaking from the damaged Nord Stream 2 pipeline in the Baltic Sea will continue for several days and perhaps even a week, the Danish Energy Authority said.

Vessels could lose buoyancy if they enter the area, and there might be a risk of leaked gas igniting over the water and in the air, but there were no risks associated with the leak outside the exclusion zone, it said.

The leak would only affect the environment in the area in which the gas plume in the water column is located, and the escape of the greenhouse gas methane would have a damaging impact on the climate.

Danish authorities asked that the level of preparedness in Denmark’s power and gas sector be raised after the leaks, a step that would require heightened safety procedures for power installations and facilities.

Author: Al Jazeera