As Bernard Madoff cools his heels in a Manhattan jail cell waiting to begin his 150-year prison sentence, legal sources believe that a number of new indictments may develop as a result of Wall Street's biggest Ponzi scheme. Madoff and his former accountant, David Friehling, are the only people charged so far in the massive investment fraud. Friehling, who was arrested in March, is amid plea negotiations, according to Manhattan Federal Court records. Tuesday, after The Associated Press reported that 10 more unnamed people could be indicted, lawyers involved in various aspects of the Madoff case pondered who might be at risk in the continuing investigation. One attorney familiar with the investigation who didn't want to be identified believes federal prosecutors could develop cases against 20 more people, including some who used to work for Madoff at his investment company on Third Avenue. A spokeswoman for the Manhattan U.S. Attorney's Office declined to comment Tuesday about the continuing investigation in the Madoff matter. But a number of lawsuits filed by special trustee Irving Picard, who is handling the bankruptcy of Madoff's business, have raised allegations that potentially could lead to criminal charges. One lawsuit started by Picard centers on Cohmad Securities Corp. and some of its officials. Cohmad was founded by Madoff and his friend Maurice "Sonny" Cohn of Manhasset, said Picard in his complaint filed last month in bankruptcy court. The company referred so many of its investment clients to Madoff that as much as 90 percent of Cohmad's reported income came from its referrals, said Picard. Picard sued Cohmad, Cohn, his daughter Marcia of Manhattan, Robert Jaffe of Florida and nine of the firm's registered representatives to recoup several hundred million dollars in profits allegedly paid by Madoff from his customer funds. However, the complaint against Cohmad also raised allegations that the company and its officials essentially knew that Madoff was reporting fictitious profits to his customers. This was done through a database that monitored the actual cash in Madoff customer accounts without considering the false profits, the Picard complaint stated. Cohmad commissions were calculated on the true value of Madoff customer accounts, according to the complaint. The Securities and Exchange Commission also sued Cohmad, the Cohns and Jaffee. Neither the Cohns nor Jaffee have been accused of criminal wrongdoing. Steven Paradise, an attorney representing Cohmad, didn't return telephone calls and an e-mail. Stanley Arkin, who represents Jaffe, said the SEC action "is unfair, baseless in the law."