Dozens of dead dolphins have been found on Bulgaria's northern Black Sea coastline, authorities said Wednesday.

Twenty-nine dead dolphins were spotted Tuesday and Wednesday near the town of Shabla, 310 miles northeast of the capital, Sofia. Another 26 corpses were found 10 days ago in the same area, the government's environmental office in the port of Varna said.

The animals most likely died of suffocation after getting entangled in fishing nets, the office said in a statement. There were no signs of violence, illness or pollution.