WASHINGTON - The National Park Service says graffiti has been found at four memorials in Washington.

U.S. Park Police officials said Tuesday that messages written in permanent marker were discovered over the holiday weekend on the Lincoln Memorial, the Washington Monument, the World War II Memorial and the D.C. War Memorial.

A spokeswoman says the message written on the Washington Monument references President John F. Kennedy's assassination and the Sept. 11, 2001, attacks.

Officials say the similarities in what's written and the handwriting lead them to believe the same person is responsible.

The agency says in a news release that the National Mall and Memorial Parks monument preservation crew is removing the graffiti using a mild, gel-type architectural paint stripper that is safe for historic stone.