A U.S. Park Service photo shows the vandalism on North Dakota’s column at the World War II Memorial. The Park Service says it is confident that with numerous treatments in the next couple of weeks, it will ultimately not be noticeable. (U.S. PARK SERVICE)

The World War II Memorial has been vandalized with spray paint, the U.S. Park Service said Tuesday.

Sometime before 10 a.m. Monday, someone sprayed graffiti on the base of the North Dakota column with dark paint. Officials said they were not certain what the graffiti said.

The Park Service said in a statement that “monument preservation experts have already made an initial treatment of the graffiti, using a light paint stripper to remove a significant portion of the damage.”

“Applications will continue until the marking is no longer detectable,” the statement said.

Park Service spokesman Mike Litterst said the cleanup would be much like that done in 2013 on the Lincoln Memorial after someone splashed green paint on its base.

That cleanup took several weeks of multiple treatments.

“That’s probably what we’re up against here,” he said.

U.S. Park Police are investigating.

Anyone with information can call 202-610-7500.