Irving Picard, the court-appointed trustee overseeing the liquidation of Bernard Madoff's investment firm, is preparing to file new lawsuits to recover funds from investors who were also duped by the Ponzi scheme, the Wall Street Journal said.

Picard told the Journal in an interview that he could end up suing about half the estimated 2,000 individual investors he has called "net winners" from their dealings with Madoff.

Investors categorized as "net winners" withdrew more money from Madoff's firm than the amount of principal they invested, the Journal said.

"The people who made money, who got more, have made money at the expense of the people who did not," Picard told the newspaper.

On July 21, Picard demanded more than $3.6 billion in damages in an expanded lawsuit against a hedge fund firm and individuals whom he said had helped Madoff run a massive Ponzi scheme.

Picard, a partner at law firm Baker & Hostetler LLP, has said that through March 31 he had recovered more than $1.5 billion of assets for Madoff victims.

Madoff was arrested on December 11, 2008, and pleaded guilty three months later to orchestrating the $65 billion Ponzi scheme.

The 72-year-old is serving a 150-year sentence in a North Carolina federal prison.