Sweden’s Coast Guard has detained the oil tanker Flora 1 as part of an investigation into a suspected mineral oil spill in the Baltic Sea east of Gotland.

A prosecutor is leading a preliminary investigation into suspected environmental crimes after the Coast Guard identified the vessel in connection with the discharge, which measured more than 12 km when detected by surveillance aircraft. The ship is now anchored south of Ystad, and the operation is being carried out with the Swedish Police.

The tanker was sailing from a port in the Gulf of Finland with a stated destination of Santos in Brazil. According to the Swedish Coast Guard, the vessel has an unclear flag status and is on the EU sanctions list.

Authorities said the ship is carrying oil and has 24 crew members on board. The suspected offense took place in Sweden’s economic zone, outside Swedish territory.

The Coast Guard said the Baltic Sea is an extremely sensitive ecosystem with zero tolerance for emissions. Under international agreements, coastal states have the authority to intervene and investigate suspected environmental and fisheries crimes in such cases.

Daniel Stenling, Deputy Head of Operations at the Swedish Coast Guard, said the action followed enhanced maritime surveillance linked to the deteriorating security situation in the Baltic Sea region. He added that authorities intervene when emissions are detected and that the investigation will determine whether further criminal suspicions arise.

The Swedish Coast Guard said this may be the first time it has been able to trace a discharge to a vessel subject to sanctions and potentially linked to environmental crime.