(CNN) The Secret Service acknowledged Friday afternoon that the man who breached White House security last week was on the grounds for more than 15 minutes.

The statement from the Secret Service came after a source told CNN earlier Friday about the length of the incident and the agency's resulting investigation.

In its statement Friday afternoon, the Secret Service offered some information about the incident and said the "investigation is ongoing," so far including more than 50 interviews and a review of radio transmissions and video footage.

The review found that the intruder climbed a five-foot fence and an eight-foot gate and then hopped a three-and-a-half foot fence while Secret Service members struggled to locate him.

House Oversight Chairman Jason Chaffetz told CNN's Wolf Blitzer on Friday that the intruder even managed to rattle a door handle at the South Portico entrance to the White House, although he did not make it inside.

"That's why we spend billions of dollars on personnel and dogs and technologies and fences and undercover people and video surveillance," the Utah Republican said. "And yet the person is able to get up close to the White House and spend 17 minutes before he's apprehended. That's unbelievable."

The Secret Service statement added that "immediate steps" had been taken, including "additional posts, technology enhancements, and response protocols."

"The men and women of the Secret Service are extremely disappointed and angry in how the events of March 10 transpired," the statement said.

The source explained to CNN earlier Friday that the intruder, Jonathan Tran, set off several alarms, but was able to avoid other sensors. The source said "the response to the alarm was lacking, and found (the suspect) vulnerabilities in the system."

They say the 26-year-old California man carrying a backpack jumped multiple fences at the White House complex and set off multiple alarm sensors before he was discovered just steps from a main door to the mansion.

Rep. Jason Chaffetz, chairman of the House Oversight Committee, sent a letter Friday to the acting director of the Secret Service, saying his committee is now investigating the incident.

He said his committee has learned of these additional allegations that weren't in the original affidavit, including triggered alarms that were ignored and that the suspect "may have moved around on the White House grounds undetected for a considerable amount of time."

Chaffetz wrote that the suspect also "may have attempted entry into the building."

"If true, these allegations raise questions about whether the agency's security protocols are adequate," he wrote.

Chaffetz asked William Callahan, the acting director, to provide documents and video related to the incident and to brief the committee on Monday at 5 p.m. ET.

A Secret Service source tells CNN that Tran was observed looming around Pennsylvania Avenue as early as 6 p.m. almost six hours before he was arrested on the White House grounds.

Video surveillance footage shows Tran, the accused jumper, first jumping a fence in the Northwest corner of the Treasury Building, immediately adjacent to the White House. Tran activated a sensor alarm in the Treasury Moat, the source said.

Secret Service officers responded to the alarm, but Tran had already snuck beyond one Secret Service post and moved closer to the White House when an officer came to investigate. The source believes Tran then crossed over the East Executive Drive and jumped the White House gate near an East Wing guard post that is not routinely staffed.

The source said Tran activated an alarm sensor, but was hiding behind a pillar of the East Wing entrance. The source said Tran then jumped a low wall before traversing along East Wing. Several sensors went off, but it is unclear if they were properly investigated. A variety of detection systems ring the White House complex in overlapping zones. The systems primarily rely on infrared and microwave technology, but can be subject to malfunction or false activation.

The incident happened just before midnight on the night of March 10 while President Donald Trump was at the White House.

The President was alerted about the intrusion late Friday night, an administration official said. Trump said last Saturday that the suspect was disturbed, calling the situation "sad" and saying he appreciates the work of the Secret Service.

"The service did a fantastic job," the President said to reporters during a lunch meeting with Cabinet officials at the Trump National Golf Club in Potomac Falls, Virginia. "It was a troubled person. It was very sad."