The crypts at St Michan’s Church in Dublin will be forced to close “for the foreseeable future” after they were vandalised and the head of an 800-year-old mummy, known as the Crusader, was stolen.

The Archdeacon of Dublin, the Ven David Pierpoint, described the vandalism of church crypts as sacrilegious and said the site, which has been open to the public since the 1930s, would be forced to close.

The break-in was discovered shortly before lunch time on Monday when a guide was preparing to open St Michan’s for visitors. The guide discovered the head of the Crusader had been severed from its mummified body and was missing.

The head of a mummified nun, who died 300 years ago, had also been turned 180 degrees to face the wrong direction while a third mummy had been turned on its side.

St Michan’s said the head of an 800-year-old mummy, known as the Crusader, has been stolen.

The crypt of the family of Irish mathematician William Hamilton was also damaged.

“They broke open that vault, it’s a big heavy steel door, and broke open one of the coffins,” the archdeacon told The Irish Times. “Parts of the contents of the coffin have been dragged out.

“These are people who have been lying at rest for years and years and to have them desecrated in such a sacrilegious way is so distressing and disturbing. I can’t put it in words, I’m quite disgusted. The likelihood is we’ll have to close these vaults and close our tourist facility.”

The vaults receive about 28,000 visitors a year. The archdeacon warned that closing the crypts would significantly affect the revenue used to maintain St Michan’s church which was founded in 1095.

The crypts were vandalised in 1996, when a number of teenagers broke into the vaults and took the bodies from their coffins, including the body of a child. “They dragged them up onto the ground and seemed to be playing football with the heads,” said Archdeacon Pierpoint. “Thankfully at that time the guards did their jobs extremely well and they caught the perpetrators.”

Services at St Michan’s Church will not run for the coming days, and the crypt will remain closed for the foreseeable future, the archdeacon said. Photograph: Tom Honan

The vaults were closed to the public for a week following the 1996 vandalism and reopened once the bodies were “reconsecrated and sealed”.

The Archdeacon was unable to confirm when the vaults would reopen following this second break-in. “We will have to keep the church closed for a few days. Services will continue as normal but as regards visitors we’ll have to put a stop for that.”

The Archbishop of Dublin also expressed outrage and shock at the desecration of remains at the ancient burial place. “Not only have these individuals desecrated the sacred crypt but they have destroyed these historic mummies which have been preserved in St Michan’s for hundreds of years,” he said.

Archdeacon Pierpoint at the crypt at St Michan’s Church. Photograph: Tom Honan.

A spokesman for An Garda Síochána said gardaí were investigating the break-in which they believe occurred between 7pm on Saturday, February 23rd and 8am on Sunday, February 24th. St Michan’s Church is on Church Street, in Dublin 7.

Gardaí are appealing for anyone with information to contact them at Bridewell Garda station on 01-6668200.