According to the Royal Opera, certain pieces of "extremely heavy hanging scenery" must be altered to adhere to British safety regulations. In a statement, officials at the company said that Muti and de Ana had refused to "accept what we think are minor scenic changes" despite several months of negotiation.
"Despite numerous solutions to this problem being suggested, Mr. de Ana showed no spirit of collaboration and rejected all options presented," read the statement, issued in the names of Pappano, director of opera Elaine Padmore, and CEO Tony Hall.
"We are totally perplexed by Maestro Muti's last minute decision given the level of cooperation, goodwill and trust shown by the Royal Opera House towards the Maestro and the Teatro alla Scala."
"These changes will not, in our view, in any way diminish the audience's appreciation of the production," the three added.
In its own press release, La Scala rejected the Royal Opera's characterization of the changes as "minor."
"It is with great regret that Riccardo Muti and Hugo De Ana have decided to withdraw from this production which is not completely faithful to their conception," the statement said. "Their decision is the result of long and careful thought and upholds the tradition of La Scala that any restaging correspond absolutely to the original production."
As a result of the "substantial changes made to the staging," the company said, the performances "will not carry the La Scala name but only be [described as] 'inspired' by the La Scala production."
It was not clear whether the Royal Opera had agreed to stop referring to the staging as a La Scala production.