No evidence has been found that securities were purchased for customer accounts at Bernard Madoff's operation in an investigation going back roughly 13 years into the purported $50 billion fraud, a court-appointed trustee said on Friday.

Irving Picard, the trustee overseeing the liquidation of Madoff's brokerage, spoke at a meeting at U.S. Bankruptcy Court in Manhattan. The meeting was for Madoff creditors who include individual investors, banks, charities and others,

Last month, the Financial Industry Regulatory Authority also said its examinations had shown no evidence of trading by Madoff's investment fund. That means Madoff either placed trades through other brokerages, a move industry officials have considered unlikely, or he was not executing trades at all.

Picard said his team now has information going back about 13 years about the accused swindler's activities, and we are getting a feel for how this operation worked.

Picard also said Madoff customers who have already submitted claims seeking to have their money returned are to receive letters in a week or two on how their claims will be treated.

About 2,350 customer claims had been filed through Thursday, he said.

Picard is working with the Securities Investor Protection Corp to liquidate Madoff's New York-based brokerage and find assets to distribute to customers who believe they were defrauded. Madoff's firm had a brokerage and an investment arm.

Madoff, 70, was charged by federal prosecutors in December with fraud. His lawyers have said he is cooperating with authorities.

(Reporting by Grant McCool and Caroline Humer, editing by Dave Zimmerman)