For more than a week, a Chinese commercial ship has apparently been forced to anchor in the Baltic Sea, surrounded and monitored by naval and coast guard vessels from European countries as the authorities attempt to unravel a maritime mystery.

The development arose after two undersea fiber-optic cables were severed under the sea, and investigators from a task force that includes Finland, Sweden and Lithuania are trying to determine if the ship’s crew intentionally cut the cables by dragging the ship’s anchor along the sea floor.

On Wednesday, the Swedish police announced that the inquiry into the episode had concluded but that an investigation was ongoing. Sweden did not release any initial findings.

American intelligence officials had assessed that the cables were not cut deliberately, though the authorities in Europe say they have not been able to rule out sabotage.

“The preliminary investigation was initiated because it cannot be ruled out that the cables were deliberately damaged,” Per Engström, the superintendent of the Swedish police, said in a statement on Wednesday. “The current classification of the crime is sabotage, though this may change.”

Denmark has said it is in “ongoing dialogue” with various countries, including China.

The mystery of the severed cable and who is to blame comes as Europe is increasingly on edge after a number of apparent sabotage operations, including arson attacks, vandalism and physical assaults. Many of these have been attributed to Russian intelligence operatives, including a plot that emerged last month, Western officials say, to put incendiary devices on cargo planes.