LEICESTER, United Kingdom – Two mysterious skeletons were found in an abbey in central England on Monday, and no one knows how they got there.

A builder was doing restoration work in the chapter house of Mount St. Bernard Abbey in Leicestershire, near the town of Coalville, when he found a cavity in the wall full of bones.

“On removing some of them it soon became apparent, to his shock, that they were human bones,” the abbey said in a statement.

“On closer inspection it could be seen that they had been used for an anatomical display as some of them were wired or screwed together and numbered. We contacted the police and after a thorough assessment of the situation they were satisfied that these were bones connected with educational or medical purposes and were not connected with any crime,” the statement continued.

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The Trappist Cistercian monastery was founded in 1835 and the chapter house was built in 1860, which is about the time the skeletons are believed to have been walled up.

The authorities gave the monks permission to bury the remains, but the decision was made to return them to their original resting place, where a small memorial will be placed. The monks will also hold a religious service for the unknown deceased.

In their statement, the abbey said: “The mystery is what were the bones doing there, who put them there and when?”

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The monks said there are no records in the abbey archives pertaining to the skeletons.

“One theory is that perhaps at the time of the construction of the chapter house we were contacted by an educational institution or hospital who no longer had any use for the bones asking if we could suitably bury them and it was decided the chapter house would be a good place for them, even though we have a proper cemetery in the grounds,” the abbey speculated.

Mount St. Bernard Abbey was recently featured in a documentary called Outside the City, which followed the monks as they opened the only Trappist brewery in the United Kingdom.

Follow Charles Collins on Twitter: @CharlesinRome