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Head of Islamic studies at Duke says he's disappointed in school's decision

(CNN) Duke University officials on Friday cited security concerns as part of the reason for the school's reversal of its decision to allow a Muslim call to prayer to sound from a campus chapel bell tower.

Neither the Durham, North Carolina, school nor the local FBI office, which was made aware of the situation at Duke, would specify details of these concerns, but Michael J. Schoenfeld, the university's vice president of public affairs, said the number and tone of the calls were "pretty loud and nasty."

"We have heard from a lot of people who have a lot of interesting and important opinions and perspectives on this," Schoenfeld said.

In a statement Thursday, the school said plans changed because its effort to "unify was not having the intended effect."

The Duke Muslim Students Association had planned to chant the call, or adhan, from the Duke Chapel bell tower. The adhan signals the beginning of the weekly prayer service. Jummah prayers have taken place in the basement of Duke Chapel for many years.

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