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30 March 2014 Last updated at 13:54 BST
The remains may be part of a massive emergency burial pit where thousands of plague victims were left 600 years ago.
Lead archaeologist Jay Carver says the find "solves a 660-year-old mystery".
"This discovery is a hugely important step forward in documenting and understanding Europe's most devastating pandemic," he said.
Skeletons unearthed in London Crossrail excavations have been found to be Black Death victims from the great disease of the 14th Century.