WASHINGTON - The US Secret Service tightened security outside the White House following an embarrassing security breach in which an intruder with a knife scaled the White House fence, ran across the lawn and made it all the way inside before agents stopped stop him.

Increased surveillance and more officer patrols are among the measures that Secret Service Director Julia Pierson has ordered as the elite agency strives to ensure such an incident can't happen again. Pierson has also launched a full investigation into what went wrong Friday evening while the first family was away from the White House.

A member of the House Homeland Committee said Sunday that it was astonishing, at a time of concerns about terrorist attacks, that "someone could actually get into the White House without being stopped."

Republican Rep. Peter King said the intrusion was "absolutely inexcusable" and he expected congressional hearings into the incident at one of the world's most heavily secured buildings.

"This demands a full investigation, an investigation as to what happened, why it happened and what's being done to make sure it never happens again," he told "Fox News Sunday."

Officials first said the fact that the intruder, identified as Omar J. Gonzalez, 42, of Copperas Cove, Texas, appeared to be unarmed may have been a factor in why agents at the scene didn't shoot or have their dogs pursue him before he made it inside.

But a criminal complaint issued late Friday revealed Gonzalez had a small folding knife with a 3-inch (9-centimeter) serrated blade with him at the time of his arrest.

At a hearing late Saturday afternoon in DC Superior Court, the assistant public defender representing Gonzalez said Gonzalez had no convictions or arrest warrants, had tested negative Saturday for drug use and had been in the military for 18 years, including three tours in Iraq, according to The Washington Post.

"This is someone who has provided service to his country and shown commitment in his life," said the lawyer, Margarita O'Donnell, as she tried unsuccessfully to get Gonzalez released.

Gonzalez was expected to appear in federal court Monday to face charges of unlawfully entering a restricted building or grounds while carrying a deadly or dangerous weapon.

According to a criminal complaint, Gonzalez told Secret Service agents after his arrest that he was "concerned that the atmosphere was collapsing" and needed to contact the president "so he could get word out to the people."

Obama and his daughters had just left the White House by helicopter Friday evening when the intruder hopped the fence. He ran toward the presidential residence unimpeded, ignoring orders from officers to stop, until being tackled just inside the doors of the North Portico _ the grand, columned entrance overlooking Pennsylvania Ave.

"Every day the Secret Service is challenged to ensure security at the White House complex while still allowing public accessibility to a national historical site," the agency said in a statement Saturday. "Although last night the officers showed tremendous restraint and discipline in dealing with this subject, the location of Gonzalez's arrest is not acceptable."

With questions mounting, President Barack Obama tried to allay concerns about whether the Secret Service is still up to the task of protecting him and his family.

"The president has full confidence in the Secret Service and is grateful to the men and women who day in and day out protect himself, his family and the White House," White House spokesman Frank Benenati said late Saturday.

He said the White House expected Pierson's review to be conducted "with the same professionalism and commitment to duty that we and the American people expect from the U.S. Secret Service."

The Secret Service said its Office of Professional Responsibility was carrying out the review.

The breach triggered a rare evacuation of much of the White House. Secret Service agents drew their weapons as they hurried White House staffers and journalists out of the West Wing through a side door.

Less than 24 hours after Gonzalez's arrest, a second man was apprehended after he drove up to a White House gate and refused to leave, Secret Service spokesman Ed Donovan said, prompting bomb technicians in full gear to search the vehicle as agents briefly shut down nearby streets.

There were no indications the two incidents were connected. But they only intensified the scrutiny of the Secret Service, which is struggling to rehabilitate its image following a series of allegations of misconduct by agents in recent years, including agents on Obama's detail.