Between 16 and 19 June, the Romanian minelayers Amiral Murgescu, Regele Carol I and Aurora laid a barrage of 1,000 mines near the port of Constanţa, (although other causes have been suggested: shells from the Romanian destroyer Regina Maria and the German 28 cms coast defense battery Tirpitz, or an accidental friendly fire torpedo attack by the Soviet submarine Shch-206.)