More than a dozen protestors were arrested Friday afternoon after blocking a highway leading to Mount Rushmore. The demonstration began several hours before Donald Trump would arrive at the national monument, where he was slated to lead a kick-off event for Independence Day weekend.

Photos of the protests show local police and National Guard members responding to the scene equipped with riot gear, gas masks, pepper spray, and smoke shells. The Sioux Falls Argus Leader reports a number of Indigenous groups participated in the demonstration, arguing that Mount Rushmore was a symbol of oppression. Activists pointed Mount Rushmore was located in South Dakota's Black Hills, which rightfully belongs to the Lakota people under the 1868 Treaty of Fort Laramie.

"Today has been a proud day to be Lakota," said NDN Collective President Nick Tilsen, who is also a citizen of the Oglala Lakota Nation. "We shut down Mount Rushmore. We put this place in lockdown for three hours and we did it in a good way. We got this power from our ancestors.”

Indigenous groups have also expressed concern over the pyrotechnics display planned for Trump's event. Wildfire experts have warned that the use of fireworks could cause a forest fire and potentially contaminate surrounding bodies of water with perchlorates. Trump dismissed these concerns earlier this year when addressing the 11-year-old fireworks ban at Mount Rushmore.

"I said, 'You mean you can't have fireworks because of the environment?'" Trump recalled telling South Dakota Gov. Kristi Noem. "... I said, 'What can burn? It’s stone.' You know, it’s stone. It’s granite. So nobody knew why; they just said, 'Environmental reasons.' So I called up our people. And within about 15 minutes, we got it approved, and you’re going to have your first big fireworks display at Mount Rushmore, and I’ll try and get out there if I can."