The Swedish National Seismic Network (SNSN) said Tuesday that it detected two explosions on Monday near the area of the Nord Stream pipelines.
The first explosion was recorded at 2:03 a.m. local time in the early hours of Monday and the second one 17 hours later, at 7:04 p.m. on Monday evening, according to SNSN.
SNSN said that one of the underwater explosions resulted in a tremor of 2.3 magnitude.
According to SNSN, the last time a similar seismological event was registered in the area was in 2016. It added that this area is not usually used for defense exercises.
The German geological research centre, GFZ, told CNN that two tremors were registered at similar times at a seismic station on the Danish island of Bornholm, again close to the reported leaks on the pipelines.
Josef Zens, spokesperson for GFZ, told CNN that the first tremor was recorded at 2:03 a.m. local time and a second was recorded 17 hours later.
Zens said that “it could not be said if there was any connection between the tremors and the leaks registered on the Nord Stream pipelines on Tuesday.”
The Swedish National Seismic Network said that warnings about the gas leaks came from the maritime administration at 1:52 p.m. and 8:41 p.m. on Monday, respectively, after ships detected bubbles on the surface.
Earlier on Tuesday, the Swedish Maritime Authority told CNN that three leaks have been identified in pipelines for Nord Stream 1 and Nord Stream 2 near Bornholm, warning vessels to maintain a distance of 5 miles (8 kilometers) from the leaks and issuing a warning for aircraft, with a safety altitude of 1,000 meters.
The Danish Defense Command said in a statement Tuesday that “following the three gas leaks on the Nord Stream gas pipelines in the Baltic Sea, prohibition zones have been established around the leaks for the sake of the safety of ship and air traffic.”
Nord Stream AG, the operator of the pipelines, in safety documents published before any news emerged of three separate pipeline leaks in one day, had said that the probability of a pipeline failure or leakage is “as low as one damage event every 100,000 years”.
The operator also said that pipeline repairs were “not expected to be necessary during Nord Stream’s minimum operational lifespan of 50 years.”
Nord Stream 1 became operational in 2012, and Nord Stream 2 was completed in 2021, but never became operational.