An undersea fiber optic cable between Latvia and Sweden was damaged on Sunday, likely as a result of external influence, Latvia said, triggering an investigation by local and NATO maritime forces in the Baltic Sea.

A subsea cable connecting Latvia to Sweden’s Gotland island is the latest cable to be damaged in the Baltic Sea. Owned by Latvia’s State Radio and Television Centre (LVRTC), the cable’s Ventspils–Gotland segment was damaged early on January 26, at depths of 100m.

The Nordic country has opened an investigation into the damage, just weeks after NATO stepped up its military presence in the area following a series of similar incidents.