Image copyright Getty Images Image caption Daniel Bonventre is one of the five former Madoff employees convicted by the jury

Five former employees of disgraced Wall Street financier Bernard Madoff have been found guilty of conspiring to help him carry out his Ponzi scheme.

The verdict was announced by a US federal jury in New York after a trial that lasted nearly six months.

The employees are Daniel Bonventre, Annette Bongiorno, Joann Crupi, Jerome O'Hara and George Perez.

Mr Madoff was convicted in 2009 and sentenced to 150 years in prison for running a $65bn (£40bn) fraud scheme.

Some experts estimate that investors lost about $20bn.

These defendants each played an important role in carrying out the charade, propping it up, and concealing it from regulators, auditors, taxing authorities, lenders, and investors Preet Bharara, US Attorney

"As the jury unanimously found, these five defendants played crucial roles in constructing and maintaining the house of cards that was the Madoff investment fraud," US Attorney Preet Bharara said in a statement.

He added that the convictions demonstrate that "this largest-ever Ponzi scheme could not have been the work of one person".

'Important role'

According to various reports, Ms Bongiorno was Mr Madoff's long-time secretary, while Mr Bonventre was his director of operations for investments and Ms Crupi an account manager.

Mr O'Hara and Mr Perez were both computer programmers.

"These defendants each played an important role in carrying out the charade, propping it up, and concealing it from regulators, auditors, taxing authorities, lenders, and investors," Mr Bharara said.

The five are the latest aides of Mr Madoff to be convicted for their role in the scheme.

Mr Madoff's brother, Peter Madoff, was sentenced to 10 years in prison in December 2012 for his role in the fraud.

Peter Madoff agreed to the 10-year sentence as part of a plea deal which stripped him of his assets, savings, home and personal property, as well as all future assets and income.

However, Bernard Madoff has repeatedly denied that his brother had any involvement in the scheme.

Mr Madoff's "investment fund" was once thought to be the biggest hedge fund in the world.