Newsweek on Monday retracted a story alleging interrogators at Guantanamo flushed the Koran down a toilet in front of detainees.

"Based on what we know now, we are retracting our original story that an internal military investigation had uncovered Koran abuse at Guantanamo Bay," editor Mark Whitaker (search) said in statement released Monday evening.

Earlier, Whitaker acknowledged the story was problematic in an apology to Newsweek's readers, but said there was no reason to retract the story.

"We're not retracting anything. We don't know what the ultimate facts are," he told The New York Times.

Newsweek did not say what caused the turnabout.

In the apology, Whitaker said that its lone source for a story accusing U.S. interrogators of flushing the Koran (search) down the toilet to rattle a detainee later said he could not recall where information about the alleged incident came from.

"We believed our story was newsworthy because a U.S. official said government investigators turned up this evidence," Whitaker wrote. "But we regret that we got any part of our story wrong, and extend our sympathies to victims of the violence and to the U.S. soldiers caught in its midst."

Protesters took to the streets in several Afghan cities last week after Newsweek published its report. American flags were burned, relief organizations were attacked and at least 16 people were killed and scores injured in clashes with police.

Angry Bush administration officials were out in force following Newsweek's admission.

Pentagon spokesman Bryan Whitman called the report demonstrably false, and that investigators at the FBI and the Southern Command have not found any evidence to support it. SouthCom is based in Miami and oversees operations at the U.S. military base in Guantanamo Bay, Cuba.

"You can't go back and undo or retract the damage that has been caused not only to this nation, but to those who have been attacked, injured or killed as a result of these false allegations," he said.

The White House, said to be outraged over the report, stopped short of outright demanding a retraction. However, a spokesman implied the magazine should take back the story.

"It's puzzling. While Newsweek now acknowledges that they got the facts wrong, they refuse to retract the story," press secretary Scott McClellan said. "I think there's a certain journalistic standard that should be met. In this instance it was not.

"This was a report based on a single anonymous source that could not substantiate the allegation that was made," McClellan added. "The report has had serious consequences. People have lost their lives. The image of the United States abroad has been damaged. I just find it puzzling."

Whitaker said that writers Michael Isikoff (search) and John Barry (search) had shown their story to two Defense Department officials but that neither commented on the alleged Koran incident. Whitman implied on Monday that no Defense officials were contacted prior to publication.

Whitaker, however, did not say that the allegations in the story were wrong, but that the Newsweek reporters' source could not pinpoint where the source obtained his or her information. He also implied that the story had no causal effect on the recent riots in Afghanistan, in which 16 people have died and dozens have been injured.

"The riots started and spread across the country, fanned by extremists and unhappiness over the economy," Whitaker wrote.

The allegations by the "knowledgeable U.S. government source" were to be included in an upcoming SouthCom review, Isikoff and Barry reported in the May 9 issue.

Defense Department officials said there are no such charges in the SouthCom report.

It was unclear if the Pentagon was going to pursue a probe into the alleged incident or drop it in light of Newsweek's admission. A SouthCom spokesman said the investigation was still open, but Whitman said he did not know if it had been closed.

While the Pentagon denies uncovering any information whatsoever about the allegations, Justice Department officials told FOX News that they shared a report with Defense about one such incident.

In the summer of 2002, a Guantanamo prisoner told an FBI agent that an interrogator there flushed the Muslim holy book down the toilet. The FBI did not confirm the allegation, but passed a report containing the detainee's statement to the Department of Defense, Justice Department officials said.

On Friday, Whitman said the Pentagon did not receive the report, and that even if Newsweek's source was based on that statement, it would be "substandard" journalism to report on a detainee's uncorroborated statement.

Eric Burns, a media analyst and host of "FOX News Watch," agreed that Isikoff and Barry should have tried to back up their source.

Journalists are supposed to "get multiple sources for printing something incendiary," and if the source's information did come from a military report, "they should have gotten a copy of that report," Burns said.

That the reporters did not find any U.S. officials who could confirm their source's information makes the "knowledgeable U.S. government" source's credibility even more dubious, Burns said.

"Who was this official they went to? Was he in a position to know?" Burns wondered.

Burns said he understood why Newsweek, in light of the Abu Ghraib scandal, was eager to go forward with the story, and that Isikoff, who has "a hell of a reputation" in journalism, was no Jayson Blair (search).

But, "The charge here is that an erroneous report led to death. If that's what actually happened and can be causally established, then there is no more serious charge you can make against a news organization, and no more bizarre explanation from one," Burns said.

He cautioned that it might be pushing it to blame Newsweek for the ongoing violence in Afghanistan, saying that despite the news weekly's blunder, "there are people who are looking for reasons to hate us ... it will have no effect on people abroad who do not care for this country's behavior."

Many of the inmates at Guantanamo were captured during the U.S.-led war against the Taliban in Afghanistan following the Sept. 11, 2001, attacks.

FOX News' Bret Baier, Anna Persky and Nick Simeone contributed to this report.