fund managers Ralph Cioffi and Matthew Tannin, who were charged on June 18 with lying to investors about the precarious state of their once-giant portfolios. BusinessWeek has learned that authorities are now examining the funds' dealings with Wall Street banks to determine whether the managers misled them as well.

Investigators are gathering more evidence about possibly misleading comments Cioffi and Tannin made to major lending and trading partners, according to people...