The National Park Service is investigating vandalism at several monuments in D.C., including one message that read "Jackie shot JFK" and another referencing Sept. 11.

A worker sprays graffiti at the Lincoln Memorial on Tuesday. (Photo courtesy National Park Service) Photo courtesy National Park Service National Park Service spokesman Mike Litterst addresses reporters Feb. 21 about three acts of vandalism report at national monuments over the President’s Day weekend. (WTOP/Kate Ryan) (WTOP/Kate Ryan) Graffiti found on the #NationalMall pic.twitter.com/89ddsdUG03 — Kate Ryan (@KateRyanWTOP) February 21, 2017 National Park Service crews work to remove graffiti from the Lincoln Memorial. (WTOP/Kate Ryan) ((WTOP/Kate Ryan)) Graffiti is shown here scrawled on the Lincoln Memorial. (WTOP/Kate Ryan) (WTOP/Kate Ryan) Graffiti is scrawled on the Lincoln Memorial. (WTOP/Kate Ryan) (WTOP/Kate Ryan) Graffiti at the Lincoln Memorial is blocked off by the National Park Service ahead of repair and cleaning. (WTOP/Kate Ryan) (WTOP/Kate Ryan) U.S. Park Police spokeswoman Anna Rose speaking to reporters in front of the Lincoln Memorial, one of three monuments where the graffiti appeared. (WTOP/Kate Ryan) (WTOP/Kate Ryan) ( 1 /7) Share This Gallery: Share on Facebook. Share on Twitter. Share via email. Print.

WASHINGTON — The National Park Service is investigating vandalism to several national monuments in D.C.

Cryptic messages scrawled in permanent marker cropped up at the Lincoln Memorial, the Washington Monument, part of the World War II Memorial and the D.C. War Memorial over the Presidents Day weekend, park service officials said Tuesday.

The graffiti at the Washington Monument was removed by Tuesday evening, the park service said via Twitter; work at the other sites will continue on Wednesday.

One of the messages found at the Lincoln Memorial read “Jackie shot JFK” and referenced the Sept. 11, terror attacks, said U.S. Park Police spokeswoman Sgt. Anna Rose. Some of the messages are illegible, she said.

“Today, it’s certainly an ugly scar,” said NPS spokesman Mike Litterst. “A month from now, the millions that come here to see it won’t even be aware that this happened.”

Earlier, Litterst told NBC Washington the messages were likely written by just one person, based on the similarity of what was written and the handwriting style.

WTOP’s Kate Ryan and Jack Moore contributed to this report.

Editor’s Note: This story was updated on Thursday, Feb. 23 to include a fourth monument that was also vandalized, the D.C. War Memorial.