[ by Melanie Gretchen ] U.S. prosecutors offered several former junior UBS AG employees immunity from criminal charges in exchange for their cooperation in the various interest-rate manipulation investigations, including the one pertaining to Libor.  UBS is a main target of U.S. antitrust officials - although it's not immediately clear which UBS executives are the main suspects.  All told, federal investigators are investigating 16 or more banks for collusion in efforts to manipulate interest rates, including Libor. Status Report. It should be noted that the proposed immunity deals do not signal that a settlement with UBS is imminent or that arrests of pending.  However, they would appear to confirm that UBS is a prime suspect.  UBS has disclosed in filings that it received leniency deals from the antitrust regulators in the United States, Switzerland, and Canada.  Nevertheless, the bank is still looking at potential enforcement action by the U.S. Justice Department's fraud section, the CFTC, and Britain's FSA (Financial Services Authority). For further details, go to [Reuters, 8/9/12].