UPDATE 1-U.S. CFTC says it is not probing Icahn's activity in biofuels credits

WASHINGTON, June 5 (Reuters) - The U.S. Commodity Futures Trading Commission informed eight Democratic U.S. senators last month that it is not investigating biofuels credits after the lawmakers had urged it to probe billionaire Carl Icahn's activity in that market, according to a copy of a letter seen by Reuters on Monday.