In the latest twist in one of the most intriguing literary mysteries in recent history, an Italian investigative journalist says financial and real estate records indicate that the Italian translator Anita Raja — daughter of a Polish Jewish mother and Neapolitan father — is behind the best-selling author Elena Ferrante.

In a report released Sunday in The New York Review of Books and in Italian, French and German publications, Claudio Gatti, an investigative journalist for Il Sole 24 Ore, an Italian business daily, reported that records show a dramatic uptick in payments from Ferrante’s publishing house in Rome, Edizioni E/O, to Raja since 2014, when Ferrante’s novels took off around the world.

In recent years, Raja’s name and that of her husband, the novelist Domenico Starnone, have been most often mentioned as possibly being responsible for Ferrante’s books because of stylistic echoes in Ferrante’s work, in Starnone’s novels and in Raja’s translations of German novels whose self-aware female narrators recall those in Ferrante’s books.

Ferrante has become an international phenomenon with her four novels set in Naples: “My Brilliant Friend” (2012), “The Story of a New Name” (2013), “Those Who Leave and Those Who Stay” (2014), and “The Story of the Lost Child” (2015). The books trace the lives of two women from their childhoods in poverty in Naples into the middle class against the backdrop of Italian postwar history, exploring the complexities of female friendship.

Gatti writes that financial records he received from an anonymous source show that payments to Raja from the publishing house increased by almost 50 percent in 2014, and in 2015 by more than 150 percent, to 7.6 million euros, or about $8.4 million. He said the payments coincided with a period in which Ferrante was likely to have received large royalty checks and that none of the publisher’s other employees or consultants saw such dramatic increases.

Reached by phone, Sandra Ozzola Ferri, one of the owners and founders of Edizioni E/O, said she had no comment on Gatti’s conclusions. “If someone wants to be left alone, leave her alone,” Ferri said. “She’s not a member of the Camorra, or Berlusconi. She’s a writer and isn’t doing anyone any harm.”

Raja could not immediately be reached for comment. Gatti reported that she had not returned messages he left for her. Both Raja and Starnone have previously denied they wrote the books.

Asked why he would want to delve into the identity of Ferrante, whose readers value her anonymity, Gatti said, “I understand that a good chunk of readers might be upset.”

He said he was doing his job as an Italian investigative journalist based in New York. “The biggest mystery outside Italy about Italy is, ‘Who is Elena Ferrante?’” Gatti said. “I’m supposed to provide answers; that’s what I do for a living.”

Beyond the financial records, Gatti cited literary clues linking Raja to Ferrante’s books, including that Nino, the love interest in the Naples novels, is Starnone’s family nickname. But his primary evidence was financial. “Raja’s work as a translator — a notoriously poorly paid occupation — can hardly account for her anomalously large income,” Gatti wrote. Raja retired last year from her day job as the head of a public library in Rome.

Gatti also said that real estate records showed that in June 2016, Starnone had purchased an 11-room, 2,500-square-foot apartment in Rome at an estimated value of $1.5 million to $2 million.

Raja, who was born in Naples in 1953, has worked as a consultant to Edizioni E/O, which has published her Italian translations of writing by the German feminist writer Christa Wolf, whose books feature complex women as narrators. Starnone’s novels often play with the notion of literary doubles and, like Ferrante’s work, feature writer-protagonists who draw on their Neapolitan roots as material even as they write to escape those roots.

This year, an Italian academic speculated that Marcella Marmo, a Neapolitan historian, might be behind the books. (Marmo denied she was.) Devoted readers have lined up for copies of Ferrante’s novels signed by Ann Goldstein, the English-language translator, as if she were a kind of sibyl in contact with the divine. A professor at the University of Padua in Italy recently called on academics to use quantitative analysis to compare Ferrante’s prose to Starnone’s.

In a deeply reported sidebar, Gatti discovered that Raja’s mother had come to Italy from Germany with her parents in 1937 to escape the Nazis. Her extended family died in the Holocaust.

But how Ferrante’s novels came into being remains a mystery that financial records alone cannot solve definitively. Was Raja the sole author of Ferrante’s books? Are they the product of collaboration, including with Starnone, as literary critics have speculated in the past, even as Ferrante’s fans have bristled?

Starnone’s name first came up in 2005, when an Italian literary critic, Luigi Galella, spotted similarities between Ferrante’s first novel, “Troubling Love,” published in Italy in 1992, and Starnone’s 2000 novel “Via Gemito.” Both are set in Naples, narrated by the guilt-ridden children of violent painter fathers who beat their seamstress wives, and some descriptions are strikingly similar.

Only one of Starnone’s novels has been translated into English: “First Execution,” published in 2009 by Europa Editions. His latest novel, “Lacci,” or “Laces,” published in 2014, tells a story of the dissolution — and reconstitution — of a marriage, but from multiple perspectives over decades, a technique favored by Wolf. Its plot echoes that of Ferrante’s 2002 novel, “The Days of Abandonment,” told from the perspective of a woman who falls apart then pulls herself together after her husband leaves her with two young children.