FBI Director Robert Mueller said Tuesday the bureau has tightened its rules for dealing with confidential informants after recent scandals on both coasts, including a retired agent's indictment on murder charges.

The unspecified changes followed embarrassing revelations of a love affair and gangland killings that an earlier overhaul of informant guidelines was intended to prevent.

"Given the circumstance in New York, the protocols relating to our handling of informants changed dramatically," Mueller told the Senate Judiciary Committee.

Retired FBI agent R. Lindley DeVecchio was indicted in March in state court in Brooklyn, N.Y., for helping a mobster, who also was an FBI informant, plot four murders in the 1990s. In Los Angeles, another informant, Katrina Leung admitted in December that she lied to the FBI about her intimate relationship with her FBI handler, James J. Smith.

Last year, Justice Department inspector general Glenn A. Fine found that FBI agents frequently violate the bureau's rules on informants.

Those rules were rewritten in 2001, after celebrated cases in which FBI agents protected mobsters from prosecution or tipped them off to investigations while simultaneously using them as FBI informants.

In one case, former FBI agent John J. Connolly Jr. tipped off Boston mobster James "Whitey" Bulger to a looming racketeering indictment, causing Bulger to flee. He remains at large.