Archaeologists have found many more human bodies at a dig next to the Cathedral.
The team from Durham University revealed last week that they had found the remains of four people on a construction site next to the Palace Green Library.
Now preliminary excavations have raised the total to eighteen.
Experts originally thought they had uncovered the remains of Durham Cathedral’s medieval cemetery, whose boundaries may have extended further than the present day burial site.
However, the bodies appear to have been thrown on top of each other rather than respectfully buried, indicating a mass burial.
Richard Annis, senior archaeologist, Archaeological Services Durham University, said: “We have found clear evidence of a mass burial and not a normal group of graves.
“One of the densest areas of the excavation was further north, which is further away from the edge of the presumed graveyard.
“The bodies have been tipped into the earth without elaborate ceremony and they are tightly packed together and jumbled.
“Some are buried in a North to South alignment, rather than the traditional East to West alignment that we would expect from a conventional medieval burial site.”
The excavation team plan to carry out further research into the remains in the New Year, including dating the bones and looking for clues as to their origin.
Mr Annis explained that no definitive explanation could be offered until this work was carried out.
“The process of post-excavation processing, examination and analysis is essential to allow us to draw proper conclusions about this group of human remains.
“It’s too early to say what they may be.”
The Ministry of Justice have given permission for further excavations to take place at the site.