The practice of having dual contracts — known as “yin and yang” contracts — is widespread in many industries in China as a way to avoid taxes, but Mr. Cui’s accusation prompted the State Administration of Taxation to announce a broad inquiry into the entertainment industry.

Its announcement did not mention Ms. Fan, but included this warning: “If violations of tax laws and regulations are found, they will be handled in strict accordance with the law.”

Mr. Cui later retreated from his initial accusations, saying he did not mean to target Ms. Fan. His ire appeared to be directed as much toward the director of “Cell Phone,” Feng Xiaogang. Mr. Cui previously had accused him of slander because the plot — in which a prominent television anchor has an affair with an assistant, played by Ms. Fan — bore striking, though he said inaccurate, parallels to Mr. Cui’s own career. A person at Mr. Cui’s office said he was no longer making any statements on the matter.

Ms. Fan denied the accusation of tax evasion — as has Mr. Feng — but she has stopped posting on her Weibo account since the tax investigation was announced. Nor has she updated her verified Twitter and Facebook accounts since she was in Cannes in May. There have been rumors of her arrest or detention — or even her flight from China.

Efforts to reach Ms. Fan or a spokesman in recent weeks proved unsuccessful.

Officials declined to comment on the status of the investigation, or whether Ms. Fan has since become a focus of it. An official with the Public Security Bureau in Wuxi, the city near Shanghai where her studio is based, refused to comment on whether the bureau had, as rumored, taken over the case.

“The situation is that we all speak with one voice from top to bottom: that is that we don’t accept interviews and we have no comment,” the official said.

Until now, at least, a partnership with Ms. Fan has been a prize for international luxury companies. She is a regular sight at red carpets and fashion shows around the world, and has a well-documented love of Louis Vuitton, Valentino and Chopard.