In 2019, Amazon.com Inc. founder Jeff Bezos accused the National Enquirer of attempting to extort him with embarrassing texts and photos, and his security team suggested that Saudi Arabia could have gleaned this data by hacking his phone.

Probes by the U.S. government haven’t led to any public action on either front.

The Federal Bureau of...

In 2019, Amazon.com Inc. founder Jeff Bezos accused the National Enquirer of attempting to extort him with embarrassing texts and photos, and his security team suggested that Saudi Arabia could have gleaned this data by hacking his phone.

Probes by the U.S. government haven’t led to any public action on either front.

The Federal Bureau of Investigation examined the possibility of a hack as part of a broad federal counterintelligence investigation into allegations of Saudi-sponsored hacking and espionage against the U.S., people familiar with the probe said. Mr. Bezos met at least once with federal investigators for that probe, the people said.

But the FBI didn’t obtain Mr. Bezos’ phone, and the investigation into whether the Saudis hacked the phone wasn’t a high priority, the people said. Though the FBI often doesn’t directly retrieve devices during an investigation, it stopped short of some technical steps—such as “jailbreaking” the phone to bypass security restrictions—and doesn’t appear to have resolved key questions about what, if anything, the Saudis did, the people said.

The Manhattan U.S. attorney’s office separately investigated whether the tabloid extorted Mr. Bezos when it threatened to publish racy photos of Mr. Bezos. It has closed the probe without bringing charges, other people familiar with the matter said.

Michael Sanchez, the brother of Mr. Bezos’ girlfriend Lauren Sanchez.

Photo: John Sciulli/Getty Images for Politicon

The people said prosecutors have determined that the source of the photos and texts was Michael Sanchez, the brother of Mr. Bezos’ girlfriend Lauren Sanchez, with whom he was having an extramarital affair.

Representatives for the Manhattan U.S. Attorney’s office and the FBI in Washington, D.C., declined to comment. Mr. Sanchez didn’t respond to requests for comment. A spokesman for Mr. Bezos declined to comment.

The government’s response marks a quiet end to a bizarre saga that captivated the business and media worlds. It is rare that a corporate executive makes public, as Mr. Bezos did, personal information about a private affair while married.

Few details about the government’s broad response to the Bezos saga with the National Enquirer have previously been reported.

Mr. Bezos first made the extortion allegations against the National Enquirer’s owner at the time in a post on the web platform Medium in February 2019. He wrote the post a month after the Enquirer published an article about his extramarital affair and quoted racy texts he sent to Ms. Sanchez.

Mr. Bezos said in the Medium post that the Enquirer’s then-parent, American Media Inc., later threatened to release the embarrassing photos of him if he didn’t call off investigators he hired to determine how the Enquirer obtained his personal text messages.

In the post, Mr. Bezos drew connections between American Media and “certain powerful people” who might have incentive to retaliate against him for the Washington Post’s coverage, including then-President Donald Trump and Saudi royals. Mr. Bezos owns the Washington Post.

Gavin de Becker, a security consultant for Mr. Bezos, said his investigators had determined that Saudis had accessed Mr. Bezos’ phone.

Photo: Kevin Winter/Getty Images

American Media merged with Accelerate 360 LLC, a Georgia-based logistics and distribution business, in 2020. A spokesman for Accelerate 360 and former American Media Chief Executive David Pecker declined to comment.

In a statement, American Media said in 2019 it “believes fervently that it acted lawfully in the reporting of the story of Mr. Bezos” and that it was acting in “good-faith negotiations to resolve all matters with him.”

In March 2019, The Journal reported that Michael Sanchez, the brother of Mr. Bezos’ lover, received $200,000 from the Enquirer’s publisher in exchange for sharing the billionaire’s secrets. The Journal later reported that federal prosecutors had evidence indicating that the text messages came from Ms. Sanchez’s phone.

A lawyer for Ms. Sanchez didn’t respond to requests for comment. In a statement provided by her attorney last year, Ms. Sanchez said of her brother: “He secretly provided my most personal information to the National Enquirer—a deep and unforgivable betrayal.”

Gavin de Becker, a security consultant for Mr. Bezos, first suggested the Saudis hacked Mr. Bezos’ phone in an opinion article published in the Daily Beast a few months after the initial Enquirer article. Mr. de Becker’s investigators had determined “with high confidence that the Saudis had access to Bezos’ phone, and gained private information,” Mr. de Becker wrote.

The New York Post published a front-page headline referring to details of Jeff Bezos’ extramarital affair in 2019.

Photo: Stephanie Keith/Getty Images

Mr. Bezos had reason to suspect the Saudis had infiltrated his phone. An official at the Manhattan U.S. attorney’s office had warned the billionaire’s security team several times in 2019 that there were security concerns with his phone and he should stop using it, according to people familiar with the matter.

Mr. de Becker, in the Daily Beast article, speculated whether the Enquirer had learned of the affair before Mr. Sanchez, and said the results of his investigation into the circumstances around the Enquirer article “have been turned over to federal officials.”

The Enquirer’s publisher had admitted in a 2018 agreement with federal prosecutors to aiding Mr. Trump during his 2016 presidential campaign by suppressing the story of a woman who said she had an affair with Mr. Trump, Mr. Bezos noted in his Medium post. He also highlighted a news report about Mr. Pecker seeking financing in Saudi Arabia for acquisitions.

Cybersecurity experts hired by Mr. Bezos concluded in a report that became public in 2020 that his phone was likely hacked by a WhatsApp account associated with Saudi Crown Prince Mohammed bin Salman. The report, by FTI Consulting Inc., drew scrutiny from cyberforensics specialists who said it didn’t explain several major technical questions about the alleged hack.

An FTI spokesman declined to comment.

Prosecutors interviewed David Pecker, then-CEO of American Media, which owned the National Enquirer, said a person familiar with the matter.

Photo: Marion Curtis/Associated Press

Saudi Arabia has previously denied the allegations about the phone hack and called them absurd. A spokesperson at the Saudi Embassy didn’t respond to requests for comment.

The FBI had already been investigating a possible hack of Mr. Bezos’ phone as part of its broader inquiry into Saudi Arabia when the FTI report was made public, a person familiar with the matter said.

“The FBI was never full throttle” on the investigation of the possible hack, the person said. Because Mr. Bezos wasn’t a member of Congress or a senior government official, the FBI didn’t view the hack allegation as an urgent national-security concern, another person familiar with the matter said.

The probe by the Manhattan U.S. attorney’s office began soon after Mr. Bezos accused the National Enquirer of trying to blackmail him. For American Media, the stakes were high. The publisher had made an agreement with the U.S. attorney’s office to avoid facing campaign-finance charges, under which it could be prosecuted if it committed any crimes in the three years after the deal.

Prosecutors interviewed American Media executives including Dylan Howard, Mr. Pecker and James Robertson, according to a person familiar with the interviews. In declarations filed in a civil lawsuit, Mr. Robertson said Mr. Sanchez was the sole source for the Enquirer’s affair article.

The suit, filed by Mr. Sanchez, alleges that the Enquirer defamed him by saying he was the sole source. The Enquirer is contesting the claim.

A July ruling in the case said that “the parties dispute” whether it was Mr. Sanchez who tipped off the National Enquirer to the affair, as American Media had said publicly, and “whether any source other than [Michael Sanchez] produced the Pornographic Materials to Defendants.”

Jeff Bezos and Lauren Sanchez attended an event in Los Angeles last month.

Photo: MARIO ANZUONI/REUTERS

—Joe Palazzolo and James Fanelli contributed to this article.

Write to Corinne Ramey at Corinne.Ramey@wsj.com, Dustin Volz at dustin.volz@wsj.com and Aruna Viswanatha at Aruna.Viswanatha@wsj.com