After a pair of explosions under the Baltic Sea, the European Union and several European governments labeled it an attack and demanded an investigation.

It could take months to assess and repair the damage to theNord Stream 1 and 2 pipes, which have been used as leverage in the West's confrontation with Moscow over Russia's invasion of Ukraine. Fears of energy shortages in Europe over the winter were heightened by the news of an attack on the lines.

The central mystery is who did it.

The leaks are the result of a deliberate act, according to the European Union's foreign policy chief. We will support any investigation that seeks to get full clarity on what happened.

Jake Sullivan is the national security adviser to the president.

The United States and most of its European allies refrained from publicly naming any suspects because of the lack of evidence. Even though the pipe carries gas, some officials speculated about how Russia could benefit.

Both Moscow and Washington denied that Russia pointed a finger at the US. The U.S. officials and experts speculated that the Baltic states might have had an interest in seeing the pipes disabled in order to send a message to the U.S.

As the war began, Germany blocked the just-completedNord Stream 2 from going into service, and Russia shut off the flow throughNord Stream 1, setting off a frantic effort in Europe to secure enough fuel to heat homes and generate electricity.

The German end of the Nord Stream 2 pipeline in Lubmin sits idle, caught up in the dispute with Russia over the war in Ukraine.Credit...Hannibal Hanschke/EPA, via Shutterstock

Some European and American officials said on Wednesday that it would be premature to conclude that Russia was behind the attacks on theNord Streams. They noted that Putin likes to show he has his finger on the gas valve, but wielding that power could mean keeping the pipes in good working order.

If the winter turns particularly cold, Mr. Putin may be able to use the undamaged Nord Stream 2 line as leverage.

Western officials and analysts said that sabotage would fit into Mr. Putin's strategy of war on multiple fronts, using economic and political tools, as well as arms, to undermine Ukraine's allies and weaken their resolve and unity. It shows how vulnerable Europe's vital infrastructure is.

Marie-Agnes Strack-Zimmermann, head of the defense committee in Germany's Parliament, said that she had no evidence that Russia was behind the attack but that it was the most plausible culprit.

She said that Putin would use every hybrid measure at his disposal to fluster Europeans.

The accusation that Russia was stupid and absurd was made by the Kremlin spokesman. He suggested that the United States was to blame for the huge profits being made by American natural gas suppliers.

The spokeswoman for the White House's National Security Council denied that they were. Russia has a history of spreading misinformation and is doing it again here.

Russian news outlets played clips of Mr. Biden saying that if the Russians invaded, there would be no moreNord Stream2. We will stop it. When Germany stopped the project, Mr. Biden was proved correct.

A photo of a patch of the Baltic Sea being churned by rising methane bubbles was captioned, "Thank you, USA," by a former Polish foreign minister.

Mr. Sikorski said that the projects bypassed Poland, which has a tense relationship with Moscow, and that Western Europe is dependent on Russia. He said that the Polish governments have been trying to stopNordstream.

He said that he shouldn't be sad. I would like to think it was our allies.

A painted map of the Nord Stream pipelines on a container near the terminal in Lubmin.Credit...Markus Schreiber/Associated Press

At a crucial time in the war, the pipelines were damaged. Kyiv is making unexpected advances in the battlefield, Moscow has challenged Ukraine's western backers with thinly veiled threats of nuclear retaliation, and Mr. Putin is ordering hundreds of thousands of men into the military.

It doesn't seem like the Kremlin would damage its assets. Prices in the gas market go up because of European fear.

Analysts don't know what Mr. Putin will lose in the short term.

The damage in the Baltic Sea won't affect European energy supplies. The Baltic Pipe is a gas conduit from Norway to Poland. It was conceived to make Warsaw less dependent on Russia.

Europe has reduced its gas consumption, found alternative suppliers and built up its stock at a steep price.

The weaponization of gas supply is not working as a political strategy according to an energy analyst. Gazprom lost most of its market share in Europe.

On Wednesday, streams of gas continued to flow out of the three pipes that had been broken. The exact cause of the leaks was being investigated by the Danes. The U.S. government was willing to help.

The German end of the Nord Stream 1 pipeline and the transfer station of another conduit, the OPAL pipeline, in Lubmin.Credit...Markus Schreiber/Associated Press

Some European officials were quick to theorize about Russian involvement, but American officials were more circumspect.

It had been tempting to blame every attack on Russia on Mr. Putin and his government. There was a widespread assumption in Washington that a major cyberattack on Albania was a Russian attempt to undermine a NATO ally.

The officials in Washington said that non-governmental actors could have committed the sabotage. Two detonations registered by seismometers in the region pointed to explosives placed by a submersible or dropped by aircraft, suggesting a state had been involved, according to others.

Does anyone benefit from it? Sauli Niinist spoke to the news outlet. This is a mystery at the moment.

They both reported from Berlin and Washington. Steven reported from Athens.