Some of Madoff's employees pursued by prosecutors

UPDATE: Now that Bernard Madoff pleaded guilty to 11 charges, prosecutors' efforts turn to identifying those who helped him perpetuate the fraud.

Investigators say Madoff told 4,800 investors in November that their accounts were worth $64.8 billion, even though he knew their holdings were a "small fraction" of that amount, according to the charges filed in Manhattan federal court Tuesday. What prosecutors still don't know is whether the employees of the firm knew these numbers were fraudulent, though investigators believe that at least some employees were involved in the fraud.