Chairman Tom Carper of Delaware said just a

Chairman Tom Carper of Delaware said just a "handful" of Secret Service members are "shaming and smearing" the agency, which employs thousands of people. He said he discussed with Pierson modifying hiring and firing rules and making other policy changes if they would help her deal with the problem.

"All of us are human, all of us have temptation and some of these jobs, they travel a lot, they're away from home a lot. They have their own foibles," Carper said. "This director is very committed to making sure there's a set of discipline policy standards to follow."

Pierson, a Secret Service veteran, is the first woman to head the agency. She was appointed to the post by President Obama about a year ago in the wake of an incident involving drinking and prostitutes ahead of the President's 2012 visit to Cartagena, Colombia.

"I have made clear to the entire workforce that I will not tolerate unprofessional behavior or misconduct at any level -- both on and off duty," Pierson told the senators, according to prepared remarks released by the Secret Service. "I remain committed to swiftly and vigorously addressing any instances of misconduct that are brought to my attention."

Pierson told the senators she has instituted several changes beyond those including appointing a chief integrity officer, centralizing the discipline process at the agency, and implementing enhanced ethics and integrity training for employees.

Sen. Kelly Ayotte, R-New Hampshire, was one of a handful of senators to go to the hour-long meeting, which was also attended by Pierson's boss, Secretary of Homeland Security Jeh Johnson.