An armed US Secret Service agent with an automatic rifle guards the White House complex during an evacuation over a security alert moments after US President Barack Obama and his family left for the presidential retreat, Camp David, in Maryland, Sept 19, 2014. [Photo/Agencies]

"This situation was a little different than other incidents we have at the White House,"Donovan said. "There will be a thorough investigation into the incident."

Only minutes before the breach, Obama had boarded his helicopter on the South Lawn with his daughters and one of their friends, who was joining the Obamas for a weekend getaway to Camp David, the presidential retreat in Maryland. First lady Michelle Obama had traveled separately to Camp David and was not at home.

It was unclear whether any other fence-jumpers have ever made it into the White House, one of the most highly protected buildings in the world. But Friday's incident was just the latest setback for an elite agency whose reputation has suffered a succession of blows in recent years.

In 2012, 13 Secret Service agents and officers were implicated in a prostitution scandal during preparations for Obama's trip to Cartagena, Colombia. The next year, two officers were removed from the president's detail after another alleged incident of sexually-related misconduct. And in March, an agent was found drunk by staff at a Dutch hotel the day before Obama was set to arrive in the Netherlands.

Obama appointed the agency's first female director last year as a sign he wanted to change the culture and restore public confidence in its operations. An inspector general's report in December found no evidence of widespread misconduct.

The Secret Service has struggled in recent years to strike the appropriate balance between ensuring the first family's security and preserving the public's access to the White House grounds. Once open to vehicles, the stretch of Pennsylvania Avenue in front of the White House was confined to pedestrians after the Oklahoma City bombing, but officials have been reluctant to restrict access to the area further.

Evacuations at the White House are extremely rare. Typically, when someone jumps the White House fence, the compound is put on lockdown and those inside remain in place while officers respond. Last week, the Secret Service apprehended a man who jumped over the same stretch of fence on the anniversary of the Sept 11 attacks, prompting officers to draw their firearms and deploy service dogs as they took the man into custody.