[3/18/17]  A California man who climbed over the White House fence last week managed to roam undetected on the grounds for about 17 minutes, as Secret Service agents appeared to ignore several alarms, officials said Friday.

The new details indicated that the episode was more serious than the Secret Service had originally stated. A Republican lawmaker said it also suggested the Secret Service’s security measures remain inadequate two and a half years after a series of lapses tarred the agency and led to major upheaval.

In a separate episode, officials also reported Friday that a Secret Service laptop was stolen from an agency vehicle in Brooklyn. But the Secret Service said in a statement about the theft that agency laptops are fully encrypted and “are not permitted to contain classified information.”

The fence-jumping episode took place on the night of March 10, and President Trump was inside the White House residence at the time.

Jonathan Tuan-Anh Tran, 26, of Milpitas, Calif., breached the outer perimeter of the White House by the Treasury Department building while carrying a backpack holding two cans of pepper spray, a book by Mr. Trump, a letter to the president and other items, the authorities said.

After an officer ultimately detained him, Mr. Tran — who appears to have a history of mental illness — said, “I am a friend of the president. I have an appointment,” according to a court filing.

“Secret Service did a fantastic job last night,” Mr. Trump said the next day.

Representative Jason Chaffetz, Republican of Utah and the chairman of the House Committee on Oversight and Government Reform, wrote in a letter on Friday to the Secret Service that the committee received “additional information” about the episode, including indications that Mr. Tran “may have moved around on the White House grounds undetected for a considerable amount of time.”