Updated

The National Park Service says the World War II Memorial in Washington has been vandalized, apparently by someone opposed to the Dakota Access Pipeline.

Park Service spokesman Mike Litterst says that some time before 10 a.m. Monday, someone spray-painted the phrase "#NoDAPL" on the North Dakota section of the memorial.

The Standing Rock Sioux tribe has been fighting along with other tribes and environmental groups to stop the completion of the $3.8 billion pipeline, saying it would threaten the water supply for millions of people. Supporters say the pipeline is a safer way to move oil than trucks and trains.

U.S. Park Police are investigating the vandalism. Litterst says a paint stripper has been used to remove much of the damage and work will continue until the paint is no longer visible.