* Experts say they have found "lost" Black Death burial site
* DNA testing found plague bacterium in skeletons' teeth
* Testing revealed curious details about victims' lives
By Andrew Osborn
LONDON, March 30 (Reuters) - Archaeologists in Britain said on Sunday they had solved a 660-year-old mystery, citing DNA tests which they said proved they had found a lost burial site for tens of thousands of people killed in medieval London by the "Black Death" plague.
The breakthrough follows the discovery last year of 13 skeletons wrapped in shrouds laid out in neat rows during excavations for London's new Crossrail rail line, Europe's biggest infrastructure project.
Archaeologists, who say the find sheds new light on medieval England and its inhabitants, later found 12 more skeletons taking the total to 25. They will further excavate the site in July to see if more bodies are buried nearby.
Last year, they said the remains probably belonged to victims of the plague, which killed about a third of England's population following its outbreak in 1348. Limited records suggest up to 50,000 victims were buried in the cemetery in London's Farringdon district, one of two emergency burial sites.
On Sunday, they said DNA testing of some of the skeletons' teeth had uncovered traces of the Yersinia pestis bacterium, which was responsible for the Black Death plague, confirming that theory.
"Analysis of the Crossrail find has revealed an extraordinary amount of information allowing us to solve a 660 year mystery," said Jay Carver, Crossrail's lead archaeologist.
"This discovery is a hugely important step forward in documenting and understanding Europe's most devastating pandemic," he added. "Until Crossrail's discovery, archaeologists had been unable to confirm the story."
Some of the victims had been buried in 1348-50, and others in the early to mid 1400s, carbon dating showed.
Testing of the remains showed that 13 of the skeletons were male, three female, and two children. The gender was undetermined in the other seven skeletons.
It also revealed information about their lives. Many had serious spinal damage, suggesting they had carried out heavy manual labour. Some had injuries to their upper bodies consistent with being involved in violent altercations.
One of the victims had also been a vegetarian; many had suffered from malnutrition. Experts said 40 percent of them had grown up outside London, possibly as far north as Scotland, showing that 14th century London attracted people from across the country, just like the British capital today.
Crossrail's Carver said the find had relevance for modern disease research.
"What's really exciting is the bringing together of many different lines of evidence to create a picture of such a devastating world event as the Black Death," he said.
"Historians, archaeologists, micro-biologists, and physicists are all working together to chart the origins and development of one of the world's worst endemic diseases and help today's researchers in ancient and modern diseases better understand the evolution of these bacteria."
Crossrail is a 15 billion pound ($24.96 billion) railway link connecting east and west London. ($1 = 0.6011 British Pounds) (Editing by Alison Williams)