Multiple countries are investigating and the authorities in Europe say they have not ruled out sabotage. But U.S. intelligence officials have assessed that the cables were not cut deliberately.

A Chinese commercial vessel that has been surrounded by European warships in international waters for a week is central to an investigation of suspected sabotage that threatens to test the limits of maritime law—and heighten tensions between Beijing and European capitals.

A Chinese ship is suspected of severing two critical internet cables in the Baltic Sea in an act of sabotage that may have been orchestrated by Russia.