Updated at 10:50 a.m. ET.
The House Homeland Security Committee chairman said Thursday Congress must question the players in the White House security breach, saying the country is fortunate it didn't turn into "a night of horror."
Rep. Bennie Thompson said before Thursday's hearing was gaveled to order that lawmakers need to talk not only to Tareq and Michaele Salahi, the couple which was admitted to the dinner without showing invitations, but also to White House social secretary Desiree Rogers. All three have declined to appear.
Thompson, D-Miss., had said Wednesday night that if the Salahis didn't show up, the panel was prepared to move forward with subpoenas "to compel their appearance."
Rep. Peter King of New York, ranking Republican on the committee, accused the White House of "stonewalling" in not permitting Rogers to appear. He told Thompson he would favor subpoenaing not only the Salahis but Rogers as well. An aide for Thompson said this morning that no decisions have been made on whether to subpoena Rogers, reports CBS News Capitol Hill Producer Jill Jackson.
Thompson said: "This hearing is not about crashing a party at the White House. Nor is it about wannabe celebrities." He said the purpose is to better protect the president.
"We're not concerned about agency embarrassment," he said. "The security gaps at issue cannot be explained away as missteps by a few frontline employees. There were undeniable planning and execution failures of the entire Secret Service apparatus," Thompson said. "We're all fortunate that this diplomatic celebration did not become a night of horror.... We must dissect every fact ... and after we do these things, we need to give thanks that no lives were lost."
Secret Service Director Mark Sullivan told the panel that "in our judgment, a mistake was made. In our line of work, we cannot afford even one mistake."
Sullivan, who had previously acknowledged a failure in procedure by his agency, was the lone witness at Thursday's hearing. "I fully acknowledge that the proper procedures were not followed ... This flaw has not changed our agency's standard, which is to be right 100 percent of the time," he said.
He said that "as an agency, we will continue to remain our harshest critic."
Defending the decision not to let Rogers testify, White House spokesman Robert Gibbs cited the separation of powers and a history of White House staff not testifying before Congress, reports CBS News Correspondent Bill Plante. Gibbs also said the first family is "quite pleased" with Rogers' performance.
In the past, at state dinners and similar events, a member of the White House social office or other White House staff stood with the Secret Service as guests entered. No one from the White House was with the Secret Service on Nov. 24. There were no plans for a White House staff member to be there, and it was the Secret Service's responsibility to make sure the guests were on the approved list.
The Salahis believe "there is nothing further that they can do to assist Congress in its inquiry regarding White House protocol and certain security procedures," their publicist, Mahogany Jones, said in a statement. "They therefore respectfully decline to testify."
The Salahis have been trying to land a part on a Bravo reality show, "The Real Housewives of D.C.," and were filmed by the Bravo show around town as they prepared for the White House dinner.
The White House has announced new guest procedures in the wake of the security breach.
"After reviewing our actions, it is clear that the White House did not do everything we could have done to assist the United States Secret Service in ensuring that only invited guests enter the complex," White House Deputy Chief of Staff Jim Messina wrote in a memo Wednesday to the staff about the new procedures.