Photo courtesy of the National Park Service

Someone vandalized the World War II Memorial yesterday, spray painting the North Dakota column with “#NoDAPL.” The National Park Service has already begun working to remove the damage, though it is still visible.

The hashtag has been part of the ongoing protest against the Dakota Access Pipeline— a light sweet crude oil pipeline currently under construction that’s slated to pass from North Dakota to Illinois and under the Missouri River on its way.

The column was vandalized some time before 10 a.m. yesterday, according to Mike Litterst of the National Park Service.

The pipeline has made national headlines following an ongoing protest by Native Americans and their allies in Standing Rock, North Dakota, on what the Standing Rock Sioux Tribe considers to be sacred land. The protesters, who identify themselves as water protectors, are worried about the effect the pipeline would have on those who depend on the Missouri River. They also say that culturally significant sites are being destroyed in the process of building the pipeline.

U.S. Park Police is currently investigating the incident. North Dakota Representative Kevin Cramer called on tribal leaders to denounce the vandalism.

NPS has already made “an initial treatment of the graffiti” with a paint stripper and removed some of the damage. It will continue to be treated until it’s totally gone.