A major undersea data cable that connects Finland and Germany, known as the C-Lion1, has been damaged, and authorities are investigating what caused the problem. The cable, which is nearly 1,200 kilometers long and runs under the Baltic Sea, was found to be broken during a routine check at around 4 AM on Monday. The damage was severe: all the fiber connections in the cable were completely cut.

The company in charge of maintaining the cable, Cinia, a Finnish state-owned provider, noticed ...