The skeletons have been eroded and no artifacts have been found inside the graves.
“Up to now ten different types of burials have been found in Burnt City, seven of which are extremely rare with only three or four examples of them in the area,” said head of the archeology team, Seyyed Mansour Seyyed Sajjadi.
“These rare burials may have belonged to emigrants, who were buried according to their own rituals,” he added.
Over 400 prehistoric sites have been excavated in Burnt City and archeologists expect the number to reach 1000.
The 5000-year-old Burnt City is located near the city of Zabol and spans an area of over 300,000 hectares.
Four civilizations have lived in the city which was burnt down three times and not rebuilt after the last fire.
The world's oldest animated picture, dice and backgammon set, the earliest known caraway seed and artificial eyeball have been found in Burnt City.