A fire broke out Monday in the Broadway theater that hosts the The Book of Mormon , forcing the long-running musical to close, at least temporarily, as the historic venue undergoes repairs.

The blaze, which began in an electrical room, caused “substantial damage” to the Eugene O’Neill Theatre, according to David Simms, New York fire department assistant chief. The cause of the fire remains under investigation.

“This was a deep-seated fire, involving a lot of electrical equipment,” Simms added. “It was very difficult to get to. There was a lot of catwalks and rigging in the theater.”

“Everyone has been safely removed from the theater,” the building’s owner, ATG Entertainment, said in a statement.…