European special services on Monday and Tuesday noticed support ships of the Russian Navy near the leaks in the Nord Stream pipelines, which were probably caused by underwater explosions, writes CNN.
It is unclear whether the ships had any relation to these explosions, these and other sources say, but this is one of the many factors that investigators will study.
According to one of the representatives of intelligence, Russian submarines were also seen near these areas last week.
Three US officials said that the United States still does not have a detailed explanation of what happened a few days after the explosions apparently caused three separate and simultaneous leaks in two pipelines on Monday.