Bosnian Commission on Missing Persons started Tuesday excavation of a pit near the eastern Bosnian Serb town of Visegrad, believed to be a mass grave. The pit at Sjemec location near Visegrad was marked as potential mass grave following an eyewitness' information, dpa reported. As Amor Masovic of the commission told local media, the pit is believed to be hiding several dozens of Bosnian Muslims from Visegrad killed by Bosnian Serb troops at early stages of the 1992-1995 war in Bosnia-Herzegovina. The excavation works at Sjemec, as the commission said, have been difficult since the entrance into the pit was mined.