(Update: Secret Service chief apologizes for how group of cancer-stricken kids was treated)

The U.S. Secret Service ordered hundreds of parents and their cancer-stricken children out of Lafayette Square on Saturday night, barricading the park for at least two hours and disrupting the group’s plans for a candlelight vigil to raise awareness of and research funding for childhood cancer, participants said.

Some of the parents and children expressed hurt and disappointment that the Secret Service and Park Police, citing security precautions, virtually shut down part of a two-day event called CureFest for Childhood Cancer.

“We ended up waiting at the gates for two hours, and they never let us in,” said Natasha Gould, an 11-year-old from Canada who started a blog after being diagnosed with an inoperable brain tumor this year. “And to be clear, the entire crowd was half kids. I cried last night in my hotel room because it was my first CureFest, and I couldn’t believe people were acting like they don’t care about children.”

In a statement e-mailed late Sunday, Brian Leary, a spokesman for the Secret Service, said the closures on Pennsylvania Avenue and Lafayette Park were “put into place based on standard [Secret Service] protocols prior to protectee movements in the vicinity of the White House Complex.”

He added, “The Secret Service would like to express its regret for not communicating more effectively with this group concerning the timeline for protectee movements in the vicinity of Lafayette Park.”

Organizers, aligned with the Truth 365 grass-roots child-cancer advocacy program, had obtained a permit to hold “A Night of Golden Lights,” in which participants would light electric candles.

But as the closure continued on, some of the sick children, fatigued by the wait or the need to receive medication, had to return to their hotel rooms, organizers said. Others began crying, and some parents became enraged. Attendees said the group of at least 700 people was not allowed access to personal items they left behind, such as chairs and blankets.

Police officers and agents on the scene told some parents that the closure was necessary because President Obama had left the White House from an entrance near the square to address the Congressional Black Caucus Foundation’s annual gala.

“At first, we were patient. I mean we’re a peaceful community; we’re fighting for kids’ lives,” said Anthony Stoddard of New Hampshire, who, after the death of his 5-year-old son, started an initiative to light public buildings in gold as a show of support for children who have cancer. “But after about an hour, or hour and a half, it started getting a little angry, some of the fathers.”

Some parents considered the park closure excessive, perhaps driven by the agency’s embarrassment over previous high-profile security lapses. Others read into it signs of a White House snub of their cause.

“I feel like this may be overcompensating for glaring errors that the Secret Service has made in past years. And again, we understand the need to keep our president safe. But we think a little consideration would have gone a long way,” said organizer Michael Gillette, a documentary filmmaker from Fairfax City, Va. “When we get shut out of the president’s front yard, it’s just disheartening.”

The candlelight vigil came about partly because of the group’s inability to persuade the White House to light up the mansion in gold as a symbol of support for the cause, as it has done for other causes, organizers said. So they decided to hold a candlelight vigil of their own. Last year was the first.

The group had a permit to stage an event from 7 to 9 p.m., Stoddard said. They had already set up a stage for speakers and an acoustic musical performance, and welcoming music had started to play, when authorities ejected them.

“Police were telling a lot of people in our group to leave because it was so close to the road there was a traffic issue. It got really frustrating. No one was giving us answers about when we would get in. So finally, about 10:30, we gave up,” Stoddard said. “It was heartbreaking.”

Staff writer Dana Hedgpeth contributed to this report.