Sweden is investigating damage to a data cable linked to Latvia, the latest breach in the Baltic Sea region where European authorities are on high alert.

Swedish prosecutors announced Sunday night that they have opened a preliminary investigation into suspected aggravated “sabotage” and ordered the detention of a vessel in the Baltic Sea suspected of damaging an underwater fiber optic cable connecting Latvia and the Swedish island of Gotland earlier that day.

By Johan Ahlander and Anna Ringstrom STOCKHOLM (Reuters) -Swedish authorities boarded a Maltese-flagged ship seized in connection with the latest breach of cables running along the bottom of the Baltic Sea to begin an investigation into the matter,

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.

A Bulgarian shipping company on Monday denied that one of its ships had intentionally damaged an underwater fiber optic cable connecting Latvia and the Swedish island of Gotland.

Sweden’s Security Service has seized a vessel suspected of damaging a subsea data cable between Latvia and Sweden early on Sunday, the third such incident in the Baltic Sea in the past three months.

After a series of suspected undersea cable cuttings, NATO has launched a new surveillance and deterrence mission to protect critical infrastructure under the Baltic Sea.

EU member states should do more to protect undersea data cables in the Baltic Sea, an EU official said on Monday, a day after an underwater fiber optic cable was damaged.

A subsea data cable between Latvia and Sweden was damaged early Sunday, sparking a criminal investigation, a third such incident in the Baltic Sea in the past three months.

Sweden on Sunday said it had seized a ship suspected of having damaged a fibre-optic cable under the Baltic Sea linking the country to Latvia, which sent a warship to investigate the latest apparent act of sabotage.