A container is floating in the sea off Arapya beach in Tsarevo municipality. Mayor Marin Kirov said all the institutions responsible for such cases have been told.
Kirov got the alert shortly before 10:00. The container can be seen from the shore, from the holiday village of houses between Arapya and Oasis.
Border Police have sent officers to the site, and the regional administration has been informed. The river basin directorate and the regional environment and water inspectorate will check whether anything has spilled.
"Absolutely everyone is coordinated," Kirov told BTA.