New York prosecutors say the multibillion-dollar fraud carried out by Wall Street swindler Bernard Madoff began as far back as the early 1970s.

The revelation comes in a rewritten indictment boosting charges against four long-time employees of the investment firm Madoff ran from his Manhattan offices.

A November 2010 indictment alleged a conspiracy to defraud Madoff's clients began in 1992.

The newly written indictment was revealed Monday. It adds new charges of bank fraud and new tax offenses to several people who worked with Madoff.

Authorities say thousands of investors lost roughly $20 billion in the fraud as Madoff failed to put their money into markets. Madoff pleaded guilty to fraud charges and is serving a 150-year prison sentence in Butner, N.C.