Little said members of Congress have not yet been briefed on the military investigation but would be "in the near future."
In a letter to Secret Service employees Monday and obtained by the AP, Director Sullivan said the agency had moved in a "swift, decisive manner immediately after this incident was brought to our attention." He praised "the overwhelming majority" of employees who he said had acted with the "highest levels of professionalism and ethical behavior."
"Our job, our mission, our responsibility is to the president, the American people and the individuals we are entrusted to protect," Sullivan said. "This is not just a matter of honor, although this is critical. It is imperative, as part of our sworn duties, to always act both personally and professionally in a manner that recognizes the seriousness and consequence of our mission."
Rep. Peter King, R-N.Y., the chairman of the House Homeland Security Committee, said in an interview Friday that the Secret Service's investigation has been moving quickly enough to satisfy him and that the resignations are a good sign.
"Secret Service is questioning anyone who has any knowledge at all," King said. "They're talking to maids, they're talking to hotel employees, they're talking to women involved, so I have faith in the investigation."
In Colombia on Friday, Colombian prosecutors spent more than three hours questioning a taxi driver who led reporters to the home of the young woman who he said was the prostitute who launched the scandal by complaining of not being paid by a Secret Service agent at the Hotel Caribe.
A senior official in the local prosecutor's office said the driver, Jose Pena, was not suspected of any crime but that a Colombian investigation into the case began Thursday to ensure that none of the prostitutes involved was a minor.
There is no information indicating a crime was committed, said the official, who was not authorized to be quoted by name.
The prosecutor's office official said the Colombian investigation was separate from U.S. probes and that Colombian investigators had not been in touch with the U.S. investigators. The official also said the Colombian investigators did not have and had not asked for a copy of the security videotapes from inside the hotel.
Pena told the AP Friday morning that he had not spoken with any U.S. investigators. He did not answer his phone after he met with Colombian investigators.
The lawyer for ousted Secret Service supervisors David Chaney and Greg Stokes, Lawrence Berger of New York, said Friday that leaks surrounding the investigations "distort the process."
Regardless of what happened inside hotel rooms, Berger said, it never jeopardized the president's security. Berger said he could not comment on the woman's claims about being paid for sex, but he added, "I don't think anything she has said is material to any of the issues I am pressing with my clients."
"Nothing that has been reported in the press in any way negatively or adversely impacted the mission of that agency or the safety of the president of the United States," Berger said.
Chaney and Stokes were forced out of the agency Wednesday. A third agent, who has not been identified and was not a supervisor, resigned.
On Chaney's Facebook account, which was made inaccessible on Friday, Chaney joked about his work with former Republican vice presidential candidate Sarah Palin while he was protecting her in 2008. The AP published a photograph it took of Chaney working in Palin's protective detail in October 2008 during a campaign rally in Carson, Calif.
"I was really checking her out, if you know what i mean?" Chaney wrote after a friend commented on the picture posted in January 2009 on Chaney's Facebook account.
Speaking on Fox News late Thursday, Palin said the joke was on Chaney.
"Well, check this out, buddy — you're fired!" Palin said.