WASHINGTON — Jamie McDaniel envisioned a simple late-night stroll along the National Mall early Friday morning, but she ended up in the center of a mystery.

She and her friend were admiring the magnitude of the marble statue of Abraham Lincoln when she noticed green paint splattered along the base.

“Is that supposed to be there?” she recalled her friend asking.

“No, this is a big thing,” McDaniel responded. She then ran to report the vandalism to Park Police about 1:30 a.m.

On Saturday, tourists again flocked to the memorial. But McDaniel’s recounting of the discovery of the defacement offered insight into the unusual case, which has startled tourists and enraged others. The memorial remains open as workers continue to wash away the stains, and authorities have released no additional details about who may have besmirched the memorial or why.

The lingering questions provide little solace to enthusiasts of Lincoln, considered one of the country’s greatest leaders, and his memorial, a well-regarded place of reverence.

“The most outrageous part about this is it happened in the first place,” said Michael Bishop, former executive director of the Abraham Lincoln Bicentennial Commission. “Is the memorial not under guard? It’s all very frustrating.”

Park Police officials declined to comment.

McDaniel, a 43-year-old matchmaker from Stafford, Va., doesn’t typically frequent landmarks in the middle of the night. An old friend from high school and her kids were visiting, so McDaniel gave her a tour of the typical tourist draws of the nation’s capital.

They decided to avoid the crowds and the heat, so they set out at night. They walked up and down the Exorcist Steps in Georgetown. They gazed at the White House. There were about 20 people touring the Lincoln Memorial upon their arrival, McDaniel said, including a rambunctious group of teenagers giggling on the steps below the 120-ton statue.

McDaniel was stunned to see green and white paint splotched along the base of the statue. She then walked around and discovered two 20-ounce Mountain Dew bottles overflowing with green and white paint, as well as white footprints near the inscription of the Gettysburg Address.

She walked around the statue and up and down the stairs until she found a police officer making rounds. The officer shut down the monument immediately, she said.

“He was in disbelief at first,” McDaniel recalled. “That’s how I felt. Why would someone deface such an important part of American history like this? It’s like someone burning a flag.”

Still concerned, McDaniel and her friend drove to the Jefferson Memorial to see if that, too, had been vandalized. It hadn’t , so they walked around to look up at the 19-foot statue of the third president. They came for the mystery but stayed for the majesty.

“Our friends keep calling us the ‘Scooby-Doo Gang’ because we thought we could get to the bottom of it,” McDaniel laughed. “But we turned it over to the police.”

On Saturday afternoon, cleaners continued washing off residue at the memorial, said Carol Bradley Johnson, spokeswoman for the National Mall and Memorial Parks division of the National Park Service. The Park Service is cleaning cautiously to prevent the statue from being besmirched any further. It is unclear when the statue will be fully cleaned.