The Lincoln Memorial was vandalized with red spray paint early Tuesday morning, and preservation crews are working to restore the historic monument, officials said.

Graffiti was found at about 4:30 a.m. on a column at the memorial, the National Park Service said in a statement. The writing was difficult to read, but “[expletive] law” appeared to have been scrawled across the pillar’s stone, according to the statement.

Additional graffiti was discovered in silver spray paint on a Smithsonian wayfinding sign in the 1400 block of Constitution Avenue, but officials said they couldn’t read what was written.

Members of the National Mall and Memorial Parks monument preservation crew had begun to remove the graffiti by Tuesday afternoon using “a mild, gel-type architectural paint stripper that is safe for use on historic stone,” according to the Park Service. The paint stripper is applied to the stone, left to set for about an hour and then rinsed clean with water.

Crew members are expected to apply treatments as necessary until the graffiti is entirely removed.

Crews also turned off an drained the water from a Dupont Circle fountain to remove graffiti and conserve the fountain, according to a Monday tweet from the Park Service.

Authorities continue to investigate the Lincoln Memorial vandalism, and anyone with additional information is asked to call U.S. Park Police at 202-610-7515.