US financier Bernard Madoff is under house arrest pending trial
The wife of US financier Bernard Madoff withdrew more than $15m (£10.4m) from an account shortly before he was put under house arrest, US prosecutors say.
Ruth Madoff withdrew $10m on 10 December, the day before his arrest, having earlier withdrawn $5.5m in late November, prosecutors said.
Her husband was arrested for an alleged $50bn fraud, and has always said he acted alone.
Prosecutors also extended Wednesday's deadline to file formal charges.
They now have until 13 March to bring an indictment.
Mr Madoff, 70, a former chairman of the Nasdaq stock exchange, is accused of running a Ponzi scheme - a system whereby early investors are paid off with the money of new clients.
Many doubt that it would have been possible to run such a large fraud without help, raising questions about why Mrs Madoff made the withdrawal, BBC correspondent Matthew Price says in New York.
If convicted, Mr Madoff faces up to 20 years in prison and millions of dollars in fines.
The financier is under house arrest while police investigations continue and has not yet entered a plea or responded to the charges.