Thirty-seven skeletons found in a mass burial site in the grounds of St John's College may not be who they initially seemed, according to Oxford researchers studying the remains.

When the bodies were discovered in the grounds of the college in 2008 by Thames Valley Archaeological Services, archaeologists speculated that they could have been part of the St Brice's Day Massacre in Oxford -- a well documented event in 1002, in which King Aethelred the Unredy ordered the killing of 'all Danes living in England'.

However, a new research paper, led by Oxford University, has thrown up a new theory -- that the skeletons may have been Viking raiders who were captured and then executed.

The skeletons were found in the ditch of a previously unknown Neolithic henge monument during excavations. They are mostly of men aged between 16 and 25 who were robust and taller than average. There is evidence that each individual was stabbed many times shortly before he died and severe wounds show they were brutally slaughtered. Some of the men also appear to have older scars, which could suggest that they were professional warriors. There is also evidence of charring on some of the skeletons, showing they may have been exposed to burning before burial.

Researchers from the Research Laboratory for Archaeology and the History of Art at the University of Oxford carried out a chemical analysis of collagen from the bones and the teeth of some of the individuals and concluded that they had had a substantial amount of seafood in their diet. It was higher in marine protein than that found in the local Oxfordshire population, as recorded in existing data.

Testing was done using strontium isotope analysis of tooth enamel, a technique which provides evidence of where an individual lived when the tooth formed. Strontium, a naturally occurring element in rocks and soils, is absorbed by plants and animals, and can be found in trace amounts in mammalian teeth. Strontium isotopes reflect the particular geological conditions so even small traces can be revealing of that individual's location.

They also looked at data relating to previous research in which an isotopic analysis of dismembered skeletons found in a burial pit at the Weymouth Ridgeway in Dorset identified the individuals as Scandinavian Viking raiders. The decapitated skeletons in Dorset, dated at between 890 and 1030 AD, and were thought to be a group of young men from different countries across Scandinavia. The isotopic analysis of the Dorset group and the individuals found in the mass burial site at St John's College show similarities.

Lead author Professor Mark Pollard, Director of the Research Laboratory in the School of Archaeology, said: 'Our latest research suggests that it is possible that the grisly remains at St John's College are the outcome of the documented massacre at St Frideswide's Church in AD 1002. Evidence of knife wounds and the burning of the bodies are consistent with the story of the burning of the church. However, following the chemical analysis of the teeth and bones, we are presented with an alternative interpretation: that they could have been a group of professional warriors, rather than a group of residents of Danish origin who were later rounded up and massacred.'