Ancient mass grave in Greece a mystery

Archaeologists discovered a mass grave in an ancient Greek cemetery, where the skeletons' wrists are clamped by iron shackles. Over 80 skeletons have been found. Archaeologists say they are victims of mass execution but there are no more details and their identities remain a mystery. However, the way they have been buried suggests that they were neither slaves nor criminals. The cemetery dates from between the 8th and 5th century BC.