U.S. authorities could announce a series of arrests in the next phase of a long-running insider trading investigation as early as next week, CNBC said in a report on Friday.

The business cable news network, without citing any sources, said it expected a significant number of arrests but offered no specifics.

On November 22, the Federal Bureau of Investigation raided three hedge funds, taking away boxes of documents. In the weeks since the raids, federal prosecutors have served subpoenas on nearly 20 hedge funds, mutual funds, investment firms and research consultants.

Sources familiar with the investigation previously have told Reuters that arrests in the probe could come before the year's end.

The investigation is loosely related to last year's arrest of Galleon Management co-founder Raj Rajaratnam and nearly two-dozen other traders, analysts and technology company executives. So far, more than a dozen people have pleaded guilty to charges of insider trading. At least a half-dozen people are known to be cooperating with the investigation.

In this new phase of the investigation, federal authorities are focusing on the misuse of confidential information provided to traders by company executives serving as consultants for so-called expert network firms.

Expert network firms are businesses that charge fees to match hedge fund managers seeking insight about an industry with a consultant familiar with a particular sector like technology or medicine.

So far, just two people have been arrested in this newest phase of the investigation. One of them is a French doctor charged with providing tips to a portfolio manager with FrontPoint Partners. Another is an official with a small California-based expert network firm called Primary Global Research.

(Reported by Matthew Goldstein; Editing by Tim Dobbyn)