Oklahoma City's Roman Catholic archdiocese said on Thursday that its archbishop and a priest performed "prayers of exorcism" to help rid the Oklahoma City Civic Center Music Hall of dangerous spirits after a satanic "black mass" was held there.

The black mass was held Sept. 21 at the venue by a satanist group known as the Dakhma of Angra Mainyu Syndicate despite protests from the archdiocese. Thousands of people demonstrated outside the event.

Archdiocese spokeswoman Diane Clay said the ancient exorcism ritual was performed the following day at the public's request. She said the archdiocese received dozens of emails and calls from people concerned about entering the building or attending events there.

"From the beginning, we have taken seriously the dark and dangerous spirits being invited into our community," Archbishop Paul Coakley said Thursday in a written statement. "To address those concerns, we visited the venue the next morning to pray prayers of exorcism over the place and to pray the prayers for cleansing."