Paris, France (CNN) -- Police are questioning France's richest woman, her lawyer told CNN Monday, as they investigate claims one of her advisers gave envelopes of cash to French President Nicolas Sarkozy and Labor Minister Eric Woerth.
Woerth and Sarkozy have both denied the allegations, which result from secret recordings that surfaced last month.
The recordings, allegedly made by L'Oreal heiress Liliane Bettencourt's butler, also refer to a bank account in Switzerland containing 80 million euros ($98.3 million), which had not been reported on Bettencourt's taxes.
Bettencourt's lawyer, George Kiejman, confirmed Monday that the heiress is being questioned by French police at her home in Neuilly, west of Paris.
Woerth will be questioned by police as well, a spokeswoman for the prosecutor's office said last week.
No date has been set for the questioning, she said. Woerth's wife, Florence, was questioned last week, the spokeswoman said.
The secret recordings published last month revealed that the minister's wife was, until late June, the deputy to Bettencourt's financial adviser.
The recordings are allegedly of conversations between the heiress and her financial adviser, Patrice de Maistre.
Bettencourt's former book-keeper, 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 repeated her allegations against de Maistre and said she regularly withdrew large sums of money at his request.
Among other claims is that Sarkozy's 2007 presidential campaign received money from Bettencourt in excess of campaign finance limits.
CNN's Saskya Vandoorne contributed to this report.