A number of 8th Century human skeletons have been found with large stones stuck in their mouths – something researchers believe locals did to stop the dead from returning to walk the Earth as zombies.

The research started more than six years ago in what was supposed to be a survey of medieval churches in County Roscommon, Ireland.

Discovery: One of the skeletons that were found in Ireland with stones stuffed in their mouths to prevent them becoming zombies

But a group of the experts stumbled on more than 120 skeletons in a cemetery which dates between the 7th and 14th centuries.

Chris Read, from the Institute of Technology in Sligo, Ireland, has been leading the team during a series of digs carried out between 2005 and 2009 at Kilteasheen, near Loch Key.

Researcher: Christopher Read lead the digs that unearthed the skeletons

He said that two male skeletons, one aged between 40 and 60 and the other a young adult probably in his twenties, had been found among hundreds of other remains.

‘One of them was lying with his head looking straight up. A large black stone had been deliberately thrust into his mouth.

‘The other had his head turned to the side and had an even larger stone wedged quite violently into his mouth so that his jaws were almost dislocated,’ he told Discovery News.

The two men were lying side by side and discovered together.

The team first thought they had stumbled across a Black Death burial ground when remains of people buried at the end of the Middle Ages had stones stuck in their mouths because they were involved in vampire slaying rituals.

It is thought about 3,000 skeletons buried from 700 to 1400 are still buried at the site.