Bosnian forensic experts began excavating Monday a mass grave found at the weekend near an abandoned coalmine in the village of Miljevina, southeast Bosnia, national radio reported. The report quoted Amor Masovic, the head of the Bosnian Commission on Missing Persons, as saying the grave could contain the remains of hundreds of Bosnian Moslems killed near Foca at the beginning of the 1992-1995 war in Bosnia-Herzegovina. About 400 Bosnian Moslems from the region were executed early in 1992 at the town's prison after Bosnian Serbs took control over the area. Most of the victims remain unaccounted for. Last week, experts exhumed the bodies of 28 Bosnian Moslems, also believed to be victims from Foca prison, at a location on the road between Miljevina and Foca.