Prosecutors, who have been criticized in recent weeks for their long inaction despite Mr. Matzneff’s avowed pedophilia, are moving on a separate track that could lead to more criminal charges.

They said on Tuesday that they would actively seek other victims of the author, and on Wednesday they raided for the second time the headquarters of Gallimard, one of Mr. Matzneff’s publishers, to seize more of his books and manuscripts, according to the French news media.

Mr. Matzneff openly talked and wrote about pedophilia, but the dynamic changed after the publication last month of “Le Consentement” (“Consent”) by Vanessa Springora, the first testimony by one of the writer’s underage victims.

Fueling an abrupt cultural shift in France, the book touched off the sudden downfall of Mr. Matzneff, who was dropped by his three publishers, stripped of a rare benefit from the French government and abandoned by longtime supporters.

On Wednesday, Christophe Girard, the deputy for culture to the mayor of Paris, released a statement on his Twitter account acknowledging that he had arranged the payment by the Yves Saint Laurent design house of Mr. Matzneff’s hotel bills in the mid-1980s, as reported by The New York Times. Mr. Girard said he had followed the instructions of Pierre Bergé, the business tycoon and partner of Mr. Saint Laurent.

Mr. Girard also wrote that it was “possible’’ that when he occupied the same position in Paris in 2002, he had written a letter of support that won Mr. Matzneff a seldom-awarded lifetime annual stipend from the National Book Center.

Until just a few weeks ago, Mr. Matzneff was recognized as a celebrated writer. He won one of France’s most prestigious literary awards in 2013. His most recent book, “L’Amante de l’Arsenal” (“The Mistress of the Arsenal”), came out three months ago in the prestigious “Collection Blanche” of Gallimard, regarded by many as France’s most distinguished publishing house. He had also enjoyed a wide audience through a column in the magazine Le Point.