Five former aides to investment manager Bernard Madoff were convicted on charges that they helped their boss conceal his massive Ponzi scheme for years.

They were all found guilty of securities fraud in connection with clients of the former Bernard L Madoff Investment Securities LLC.

Former director of investments Daniel Bonventre, portfolio managers Annette Bongiorno and JoAnn Crupi and computer programmers Jerome O'Hara and George Perez were also convicted of conspiring to defraud those clients.

The case was the first to reach trial since Madoff's arrest in December 2008 and lasted more than five months.

Prosecutors introduced into evidence thousands of pages of internal documents seized from Madoff's investment firm and called dozen sof witnesses.

Madoff is serving a 150-year-prison sentence after pleading guilty to running a Ponzi scheme.

Investors lost principal estimated at more than $17 billion.