PARIS (AFP) - French investigators have detained the estranged wife of ex-budget minister Jerome Cahuzac - who resigned in March over undeclared bank accounts - for questioning in a tax fraud probe, a source close to the investigation said on Thursday.

Dr Patricia Cahuzac was taken into custody on Wednesday and was to be questioned by anti-fraud police in the western Paris suburb of Nanterre, the source said.

The dermatologist, and her husband, a former plastic surgeon, ran a flourishing hair transplant salon in Paris. Dr Jerome Cahuzac also served as an adviser to several pharmaceutical companies.

The disgraced former minister, whose tasks in Socialist President Francois Hollande's cabinet included battling tax fraud, initially denied allegations by French investigative news website Mediapart that he had funds in a Swiss bank account.

But he did a U-turn when prosecutors opened an official probe into the undeclared overseas account said to contain around 600,000 euros (S$990,180).

He resigned on March 19 and has admitted to having the account for some two decades, in a scandal that dealt a major blow to Mr Hollande's government.

A retired tax inspector, Mr Remy Garnier, told a parliamentary investigation panel that he has met with two private investigators hired by Dr Patricia Cahuzac, probably in connection with proceedings in her ongoing divorce from Dr Cahuzac.

Both investigators were aware of the undeclared accounts, Mr Garnier said.

A former official with Swiss bank Reyl et Cie who claimed he knew of 15 French politicians and "big names" with hidden bank accounts in the tiny Alpine country has meanwhile submitted the list to French investigators.

Mr Pierre Condamin-Gerbier said the list, submitted Tuesday, included "personalities far better known to the public than Cahuzac".