A year ago, the National Enquirer devoted 11 pages to a blockbuster story about the world’s richest man, Jeff Bezos, and his extramarital affair with former local television host Lauren Sanchez.

The story started a fevered hunt to determine how the tabloid managed to pull off the audacious scoop. That search has involved federal investigators, tabloid techniques and scandal mongering, a private investigation by Bezos and, most recently, a report from the United Nations that asserts that the Amazon founder and chief executive was a target of phone hacking by the Saudis in part because he owns The Washington Post and its opinion-page coverage of the regime had been critical.

Despite the multipronged investigations, unanswered questions remain about how the Enquirer and parent company AMI obtained the story.

Three people close to AMI, who were not authorized to speak publicly, say that Lauren Sanchez’s brother Michael Sanchez — a talent manager in Hollywood who had previously placed stories in AMI publications — is the only source for their report on the Bezos affair. But the Bezos investigation, as echoed by the U.N. report, asserts that it has evidence of a Saudi hack of his phone. The investigation stopped short of connecting the hack of Bezos’s phone to the Enquirer report.

Months after the alleged hack, Post columnist Jamal Khashoggi, who was a prominent critic of the Saudi kingdom, was slain at the Saudi Consulate in Istanbul in October 2018 by agents of the Saudi government.

Attention on the U.N. report, which explained how Bezos’s iPhone X was apparently hacked, spurred a spate of news stories last week and a renewed declaration from AMI that its story on Bezos was not based on an international hack but on a much more pedestrian source.

“The single source of our reporting has been well documented,” AMI said in a statement to The Post. “In September of 2018, Michael Sanchez began providing all materials and information to our reporters. Any suggestion that a third party was involved in or in any way influenced our reporting is false.” The Post has previously reported that Sanchez provided texts to the Enquirer for its reporting on the affair.

Indeed, in October 2018, Michael Sanchez and AMI entered into a nondisclosure agreement “concerning certain information, photographs and text messages documenting an affair between Jeff Bezos and Lauren Sanchez,” according to three people who have reviewed the agreement. The existence of the contract was first reported by the New York Times. One of those people also confirmed a Wall Street Journal report that federal prosecutors who are investigating whether the Enquirer tried to extort Bezos have reviewed the text messages that Lauren Sanchez allegedly gave to her brother and that he then provided to the tabloid.

A spokesman for the U.S. attorney’s office in Manhattan declined to comment. A spokesman for Bezos, Jay Carney, declined to comment.

Disclosing the identity of an anonymous source is an unusual step for a tabloid, but AMI is under legal pressure to prove that it did not do anything illegal in its reporting on the Bezos affair.

AMI reached a deal with prosecutors in September 2018 in which it admitted to paying hush money in the 2016 presidential campaign to protect Donald Trump from allegations that he had an extramarital affair with Playboy model Karen McDougal. David Pecker, AMI’s chief executive, has a long relationship with Trump and has devoted many issues to promoting candidate Trump and attacking his rivals.

That deal protected the company from prosecution as long as it did not break any law for three years.

After the story on Bezos’s personal life, federal prosecutors in New York questioned AMI officials and people around Bezos and Sanchez to determine whether AMI engaged in anything illegal while working on the story.

Meanwhile, Bezos began conducting his own investigation to determine how his texts ended up in the tabloid. A week after the Enquirer’s story, Bezos wrote an extraordinary post on the online publishing platform Medium alleging that the Enquirer threatened to publish intimate pictures of him unless he backed off his investigation.

Michael Sanchez declined to comment for this report but referred to a statement he provided to The Post last year, saying that he would not “dignify” with a response “baseless smears” that he provided AMI with any of the couple’s text messages. He emphatically denied providing explicit photos of Bezos, which so far have not appeared in any publication.

After Bezos’s Medium post, AMI’s board announced plans to investigate Bezos’s claim that he had been the subject of a blackmail attempt by AMI. Subsequently, the company announced a plan to sell the Enquirer to Hudson Media. That deal, announced in April 2019, still has not closed.

The Enquirer’s multiple stories on the Bezos affair relied on text messages between Bezos and Sanchez and on candid photos taken from a distance. But in emails to Bezos that the billionaire posted on Medium after the story published, AMI chief content officer Dylan Howard threatened to release intimate photos of Bezos, which he considered extortion and blackmail.

The U.N. report was based in part on an investigation conducted by FTI Consulting, a global business advisory firm hired by Bezos’s attorney. The report does not establish a connection between the removal of data from Bezos’s phone and the story on his affair, but neither does it definitively rule one out.

Bezos’s personal security consultant Gavin De Becker early on accused the Saudis of hacking Bezos’s phone. What connection any alleged hacking of Bezos’s phone has to the Enquirer articles is still a mystery.

“It’s possible that the Saudis hacked Bezos’s phone and Michael Sanchez independently got the photos from his sister and some people were trying to get paid and some people were trying to get Bezos,” said a person with knowledge of the investigation who was not authorized to speak publicly about its progress. “It’s not like there’s just one explanation.”

Last week at the Sundance Film Festival, Oscar-winning director Bryan Fogel, who previously investigated Russian doping with the film “Icarus,” unveiled a documentary about the Khashoggi killing called “The Dissident.”

The film prompted renewed questions about what connection there might be between Khashoggi’s death and the tabloid story.

The U.N. report’s release, which was reportedly moved up because of the imminent premiere of the film, said that a forensic probe of Bezos’s phone conducted by FTI “suggests the possible involvement of the Crown Prince [Mohammed bin Salman] in surveillance of Mr. Bezos, in an effort to influence, if not silence, The Washington Post’s reporting on Saudi Arabia.”

At a meeting of world leaders in Davos, Switzerland, last week, Saudi foreign minister Prince Faisal bin Farhan Al Saud called the U.N. report “absurd.” “The idea that the crown prince would hack Jeff Bezos’s phone is absolutely silly,” the official said.

In a statement released Wednesday with the U.N. report, human rights investigators Agnes Callamard and David Kaye called for the United States and other nations to probe the alleged hacking of Bezos’s phone as part of a larger look at what they called “the continuous, multiyear, direct and personal involvement of the Crown Prince in efforts to target perceived opponents.”

Marc Fisher contributed to this report.