People demonstrating at North Dakota's Access Pipeline protest have expressed frustration at white demonstrators who are reportedly turning up to "colonise" the camp.
Concerns have been raised by protestors on social media, who claim that people are arriving at the Standing Rock demonstration for the "cultural experience" and treating it like Burning Man festival.
Protestor Alicia Smith wrote on Facebook: "On my way back from the camps. Need to get something off my chest that I witnessed and found very disturbing in my brief time there that I believe many others have started to speak up about as well.
"White people are colonizing the camps. I mean that seriously. Plymouth rock seriously. They are coming in, taking food, clothing and occupying space without any desire to participate in camp maintenance and without respect of tribal protocols.
"These people are treating it like it is Burning Man or The Rainbow Gathering and I even witnessed several wandering in and out of camps comparing it to those festivals."
Ms Smith observed that many protestors appeared to be living off the native American community, and were taking advantage of donations sent in for the cause. Another Twitter user said they had witnessed a protestor turn down tap water to spend donations on 'fluoride free' water.
An open letter detailing the camp's ground rules has been shared on Twitter in an attempt to tackle the issue, which reminds demonstrators that the camp is "not a vacation".
It says protestors should avoid drugs and alcohol, engage with the elders, and refrain from playing guitars around campfires.
A similar note is being shared on Facebook from Jon Petronzio, who said that there had been a "huge influx" of "mostly white" people arriving at the camp.
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Mr Petronzio urged demonstrators to remember that they are not on vacation and to help by carrying supplies and speak to the elders who are "pillars of this community".
The North Dakota Pipeline protest was sparked by plans to construct a 1,170-mile long pipeline which would run across four states. Energy Transfer Partners, the company behind the pipeline, says that it has taken measures to prevent leaks, and that there is no archaeological significance to the area.
Thousands of people have been gathering to support the Standing Rock Sioux tribe in their legal battle against the plan.
On Saturday activists protesting the continued construction of the pipeline were told to shut down one of their camps by 5 December in a letter sent to the Standing Rock Sioux Tribe's leader by the Army Corps.
Tribal leader Dave Archambault and other protest organisers have made it clear that they intend to stay in the Oceti Sakowin camp — one of three camps near the construction site — which would have been shut down.
"We are wardens of this land. This is our land, and they can't remove us," protester Isaac Weston, an Oglala Sioux member from South Dakota, told AP on Saturday.
"We have every right to be here to protect our land and to protect our water."
However US authorities said on Sunday that they had no plans to forcibly remove activists.
The US Army Corps of Engineers, which manages the federal land where the main protest camp is located, said in a statement that anyone who remained would be considered unauthorised and could be subject to various citations.
It also said emergency services might not be adequately provided to the area.
"The Army Corps of Engineers is seeking a peaceful and orderly transition to a safer location," the statement said.
"This will reduce the risk of harm to people in the encampments caused (by) the harsh North Dakota winter conditions."
High profile supporters who have expressed their support for the cause include Katy Perry, Orlando Bloom, Lupita Nyong'o, Whoopi Goldberg and Mark Ruffalo.
A GoFundMe page recently raised more than $1 million after aiming to reach just $5,000.
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