Paris, France (CNN) -- Police questioned a financial adviser to L'Oreal heiress Liliane Bettencourt on Friday as part of an ongoing investigation into his client's finances.
It is the third time in the past two weeks that police have questioned Patrice de Maistre in the case.
Police questioned French Labor Minister Eric Woerth in connection with the investigation Thursday.
The case centers on claims that de Maistre gave envelopes of cash to Woerth and French President Nicolas Sarkozy, in some cases allegedly in violation of campaign finance laws.
Woerth and Sarkozy have both denied the allegations, which were made in secret recordings that surfaced last month.
The recordings, allegedly made by Bettencourt's butler, also refer to a Bettencourt bank account in Switzerland containing 80 million euros ($98.3 million), which had not been reported on her taxes. Bettencourt is France's richest woman.
Woerth's wife, Florence, was questioned last week. The secret recordings published last month revealed that she had been de Maistre's deputy until late last month.
Bettencourt's former bookkeeper, Claire Thibout, elaborated on the allegations in an interview this month with a French investigative website.
She said she prepared envelopes of cash that were to be given to Sarkozy and Woerth, who previously worked in the Budget Ministry and was in charge of reforms to France's retirement system.
Thibout's lawyer told French news agency Agence France-Presse this month that de Maistre once asked his client for 150,000 euros ($188,800) and said he would give it "discreetly" to Woerth at a dinner.
Thibout testified before a judge about the allegations earlier in July.
The French newspaper Le Monde published her testimony, in which she said she regularly withdrew large sums of money at de Maistre's request.