Citing safety concerns, Flatiron Books has canceled the remainder of Jeanine Cummins’ author tour for her controversial novel American Dirt, Publishers Weekly reports.

The move is a stunning reversal for Flatiron, which had heavily hyped the immigration-themed novel in the months before its release. The cancellation of the tour comes days after some bookstores called off events featuring Cummins on their own accord.

In a statement, Flatiron publisher Bob Miller said the tour was scrapped because they had received “specific threats to booksellers and the author.”

Miller also admitted that Flatiron had made some mistakes promoting the novel. “On a more specific scale, we made serious mistakes in the way we rolled out this book,” he said. “We should never have claimed that it was a novel that defined the migrant experience; we should not have said that Jeanine’s husband was an undocumented immigrant while not specifying that he was from Ireland; we should not have had a centerpiece at our bookseller dinner last May that replicated the book jacket so tastelessly. We can now see how insensitive those and other decisions were, and we regret them.”

In other developments, more than 120 authors signed an open letter to Oprah Winfrey urging her to reconsider the novel as her latest book club pick.

“In light of all the good that you have done, we believe that American Dirt by Jeanine Cummins should not be honored as your book-club pick,” the authors wrote in the letter, which was posted on Literary Hub. “In the informed opinions of many, many Mexican American and Latinx immigrant writers, American Dirt has not been imagined well nor responsibly, nor has it been effectively researched.”

Authors who signed the letter include Jennine Capó Crucet, Alexander Chee, Carolyn Forché, Valeria Luiselli and Tommy Orange.

But at least one author is standing by her early support of the book. Mexican American novelist Sandra Cisneros (The House on Mango Street), who contributed a blurb for the book, said she still thought the novel had the potential to change minds, the Los Angeles Times reports.

“It’s going to be [an audience] who maybe is undecided about issues at the border,” Cisneros said. “It’s going to be someone who wants to be entertained, and the story is going to enter like a Trojan horse and change minds. And it’s going to change the minds that perhaps I can’t change.”

Michael Schaub is an Austin, Texas–based journalist and regular contributor to NPR.