* Three portfolio managers, 1 analyst to be charged - US
* U.S. Attorney to announce charges at news conference (Adds background on insider trading investigations, )
NEW YORK, Feb 8 (Reuters) - Three hedge fund managers and a hedge fund analyst will be charged with insider trading, U.S. prosecutors said on Tuesday, the latest development in a broad probe of funds' trading activities.
The U.S. Attorney in Manhattan said a press conference would be held at noon (1700 GMT) to announce the charges. FBI and U.S. Securities and Exchange Commission officials were also scheduled to attend.
Names of the defendants and other details were not immediately available. Prosecutors said two of the portfolio managers would also be charged with obstruction of justice.
The U.S. government has launched a broad investigation into insider trading, focusing recently on the activity of so-called expert network firms that match industry consultants with hedge funds to provide research and consulting advice.
Since late November, federal prosecutors have charged eight people linked to expert network firm Primary Global Research with illegally helping provide confidential corporate information to hedge fund traders and analysts. An independent technology consultant in California has also been charged.
None of the defendants named publicly in the expert networks probe so far has been a hedge fund employee.
The U.S. Attorney's office and the SEC declined to comment. FBI representatives did not immediately return calls. (Reporting by Martha Graybow and Jonathan Stempel; Editing by Lisa Von Ahn and John Wallace)