Sonja Kohn looks an unlikely villain — if she is one, that is. A strictly Orthodox mother-of-five and grandmother of 24, she is the daughter of Holocaust refugees and is unmissable in her bright, bouffant sheitel.

But it has emerged that prosecutors here and in the US are investigating whether she was paid more than $40 million (£24.5m) by Bernard Madoff for funnelling funds into his pyramid scheme through the bank she owned, Bank Medici AG. A seperate investigation is ongoing in Austria.

Mrs Kohn, 60, and the bank strenuously deny the charges, claiming they are Madoff’s victims, and there is no indication that she knew he was running a Ponzi scheme. But while Mrs Kohn is trying to rebuild her reputation — renaming her bank 20.20 Medici after it had its licence revoked in May — she has been keeping a low profile, at one point even going into hiding. The New York Times says this may be because she is afraid of retribution from Russians whose funds made up part of the $2.1 billion that Bank Medici reportedly invested with Madoff.

Mrs Kohn was born in Vienna in 1948 to parents who had come from Eastern Europe after the war. She married Erwin Kohn, and they established an import-export firm, moving to Milan and then Switzerland, developing a large international network.

Known for her aggressive manner, she founded the Bank Medici in Vienna in 1984 (it was relaunched in 2003), and a year later moved again; to New York. After she founded a small brokerage firm, Eurovaleur Inc, she quickly became known as “Austria’s woman on Wall St” — and met Madoff.

The Kohns were living in Monsey, a middle-class suburb of New York with a large strictly Orthodox community. Their wealth was unusual. “There are plenty of Wall Street folk living in Monsey,” a representative of a local synagogue said. “But there are no multi-millionaires.”

Mrs Kohn gradually became more religious, and took to wearing her distinctive wig.

From the 1990s, she divided her time between the US and Austria, where she belonged to a small Orthodox shtibl in the first district of Vienna. Founded by a group of religious Holocaust survivors shortly after the war, this shtibl has been half-jokingly called one of the wealthiest synagogues in Europe, since nearly all its members are successful Viennese Jewish families. In 1999 she was given the order of merit for services to the Republic of Austria, particularly in the financial sector. She also visited Israel several times a year and owns a house in the Jerusalem neighbourhood of Nachlaot.

There were business interests there, too. In 1999, she bought a 26 per cent stake in the Alon venture capital fund which specialised in high-tech companies, and served as a director. Mrs Kohn’s involvement in the fund attracted other foreign investors and 2004 the fund was sold to the British Jupiter group.

Together with her partner, Bank Austria, Mrs Kohn invested in the holding company Kur Futures Markets. Her only known investment today in an Israeli company is in investment company Goldhar and Co.
Her private life remains something of an enigma. In Monsey, none of her neighbours would comment. Nor would anyone in Vienna.

According to the New York Times, she patronised a number of European charities, which allowed her to “rub elbows with wealthy potential clients”.

But in Vienna, community figures say she gave mainly to the strictly Orthodox community (including some, perhaps, as an interest-free loan). The Kohns did dedicate and donate the first Sefer Torah to the European Jewish Community Centre at the EU in Brussels.

Last December, her bank disclosed a $1.2 billion loss, which it blamed on Mr Madoff. It had invested billions in his scheme, through several funds.

In February, the Austrians began to investigate whether Mrs Kohn had accepted money in order to direct investors towards Mr Madoff.

Investors are also suing Medici in Austria and the US. Mrs Kohn is reportedly co-operating with the authorities.