A U.S. grand jury on Tuesday indicted Galleon hedge fund founder Raj Rajaratnam and co-defendant Danielle Chiesi on charges of securities fraud and conspiracy in an insider trading case involving employees of some of America's best-known companies, the Reuters reported.

The indictment in Manhattan federal court, two months after the pair were charged along with others in a coast-to-coast probe on Oct. 16, lists 17 counts of conspiracy to commit securities fraud and securities fraud.

The billionaire Rajaratnam, a U.S. citizen who is free on $100 million bail, is the most prominent figure in what U.S. prosecutors described as the biggest hedge fund insider trading case ever. The government said investigators used wire taps, tactics historically used in organized crime probes, to gather evidence.

Most of the accused had expertise in tech stocks, and the allegations included passing inside information on earnings announcements, takeovers and contracts on 10 companies, generating more than $30 million in illegal profits, according to prosecutors. They alleged that Rajaratnam and Chiesi made $20.8 million in illegal profits.