WASHINGTON — The embarrassing disclosures about lapses in presidential security just keep coming for the Secret Service.

Despite more than three hours of questioning by House lawmakers on Tuesday, Secret Service Director Julia Pierson neglected to mention another security breach that occurred just days before a knife-carrying Army veteran climbed over the White House fence and sprinted into the executive mansion.

On Sept. 16, an armed security contractor with three convictions for assault and battery rode on an elevator with President Barack Obama and his security detail at the Centers for Disease Control and Prevention in Atlanta, violating Secret Service protocol. The Washington Examiner and The Washington Post reported the details of that breach just hours after Pierson left a House hearing.

A Secret Service spokesman confirmed the Atlanta elevator incident late Tuesday but did not elaborate, citing an ongoing investigation of the episode. It was not clear whether the president or Pierson herself knew about the incident until recently.

Pierson got a vote of low confidence from the lawmakers, who called for additional reviews into the agency’s poor response. The chairman of the House committee with oversight responsibilities for the Secret Service called for an independent commission to do a “top-to-bottom” review of the agency.

“I am deeply concerned with the lack of transparency from the Secret Service regarding the recent security breach at the White House,” Rep. Michael McCaul, R-Texas, the chairman of the House Homeland Security Committee, said of the Sept. 19 incident. “This latest episode adds to the growing list of failures from an agency plagued by operational challenges, cultural problems and reporting difficulties.”

At Tuesday’s hearing, Pierson said she is the one who briefs Obama on threats to his personal security and said she had briefed him only once this year, “for the Sept. 19 incident.” She also disclosed that shortly before the alleged intruder, Omar J. Gonzalez, scaled the fence at least two of her uniformed officers recognized him from an earlier troubling encounter but did not approach him or report his presence to superiors.

On Aug. 25, Gonzalez was stopped while carrying a small hatchet near the fence south of the White House, Pierson said.

Lawmakers were aghast, too, about a four-day delay in 2011 before the Secret Service realized a man had fired a high-powered rifle at the White House, as reported by the Post on Sunday.

Pierson told the hearing the security plan for protecting the White House was not “properly executed” on Sept. 19 when the intruder sprinted across the White House North Lawn and through the unlocked front door of the mansion, knocking over a Secret Service officer and then running past the staircase that leads to the first family’s residential quarters. He ran through the East Room before being tackled by a Secret Service agent near the entrance to the Green Room. The Post reported Tuesday that the agent was off duty at the time and just happened to be in the area.

The Secret Service’s story about the extent of that breach changed late Monday night after the Post reported that Gonzalez got well past the front door of the White House. Previously it had said Gonzalez had been stopped just inside the front door. After hours of questioning Tuesday, it remained unclear what and when Pierson and Homeland Security Secretary Jeh Johnson knew about the incident. The Secret Service is part of the Homeland Security Department.

Three days after the breach, Johnson described it as “events on the North Lawn of the White House.”

No one has been fired or demoted since the Sept. 19 White House intrusion.

Pierson said she was conducting an internal review to determine the facts. Wednesday marks day 12 of that review. Pierson did not say when it was expected to be completed, but said the results would guide any security adjustments and personnel actions “that are necessary to properly ensure the safety and security of the president and first family and the White House.”

Gonzalez was indicted Tuesday and was scheduled to appear Wednesday before Magistrate Judge Deborah A. Robinson in U.S. District Court.