RICHMOND, Va. (AP) -- A Rolling Stone magazine article about an alleged rape on the University of Virginia campus was a "story of journalistic failure that was avoidable," the Columbia University Graduate School of Journalism said in a report published Sunday night. "The failure encompassed reporting, editing, editorial supervision and fact-checking," said the report, which was posted on the journalism school's and magazine's websites. Rolling Stone Managing Editor Will Dana posted an apology on the publication's website and said the magazine was officially retracting the story. "We would like to apologize to our readers and to all of those who were damaged by our story and the ensuing fallout," Dana wrote. The article's author, Sabrina Rubin Erdely, did not answer a telephone call from The Associated Press. Rolling Stone had asked for the independent review after numerous news media outlets found flaws with the November 2014 story titled "A Rape on Campus." The article focused on a student identified only as "Jackie" who said she was raped by seven men at the Phi Kappa Psi fraternity house more than two years earlier. It also described a hidden culture of sexual violence fueled by binge drinking at one of the nation's most highly regarded public universities. Charlottesville Police Chief Timothy Longo said at a March 23 news conference that his investigators, who received no cooperation from Jackie, found no evidence to support either. The article prompted protests on the Charlottesville campus, but the story quickly began to unravel. Other news organizations learned that Erdely had agreed not to contact the accused men. Three of Jackie's friends denied the writer's assertion that they discouraged the alleged victim from reporting the assault, and the man described as the person who led her to an upstairs room in the fraternity house to be raped could not be located. By Dec. 5, Rolling Stone acknowledged that "there now appear to be discrepancies in Jackie's account." Dana and Erdely have said they had been too accommodating of requests from "Jackie" that limited their ability to report the story because she said she was a rape victim and asked them not to contact others to corroborate, the report said. However, Columbia's report said, Rolling Stone also failed to investigate reporting leads even when "Jackie" had not specifically asked them not to. "The editors made judgments about attribution, fact-checking and verification that greatly increased their risks of error but had little or nothing to do with protecting Jackie's position," it said. The report said Rolling Stone's article may cast doubt on future accusations of rape. It also damaged the reputation of the Phi Kappa Psi chapter at U.Va. and depicted the university administration as neglectful. It also concluded that while Rolling Stone's editorial staff has shrunk by 25 percent since 2008, the problem was not a lack of resources. "The problem was methodology, compounded by an environment where several journalists with decades of collective experience failed to surface and debate problems about their reporting or to heed the questions they did receive from a fact-checking colleague," it said. The fraternity has called the article defamatory and said it was exploring its legal options. "These false accusations have been extremely damaging to our entire organization, but we can only begin to imagine the setback this must have dealt to survivors of sexual assault," said Stephen Scipione, president of the Virginia Alpha Chapter of Phi Kappa Psi, after the Charlottesville police suspended their investigation. In his apology, Dana said that magazine officials are "committing ourselves to a series of recommendations about journalistic practices that are spelled out in the report." Despite its flaws, the article heightened scrutiny of campus sexual assaults amid a campaign by President Barack Obama. The University of Virginia had already been on the Department of Education's list of 55 colleges under investigation for their handling of sex assault violations. The article also prompted U.Va. President Teresa Sullivan to temporarily suspend Greek social events. Fraternities later agreed to ban kegs, hire security workers and keep at least three fraternity members sober at each event.