Facebook users appear to be joining the fight to block the Dakota Access Pipeline. By Monday (31 October), thousands of users had checked in at the Standing Rock Indian Reservation in a bid to help protesters trying to stop the construction of the $3.7bn (£3bn) pipeline.

A post circulating the social network encouraged Facebook users to check in at the protest site to deter law enforcement officials from targeting them. As such, users have been checking in to Standing Rock, North Dakota and then posting a second message to explain why they are checking in.

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"The Morton Country Sheriff's Department has been using Facebook check-ins to find out who is at Standing Rock in order to target them in attempts to disrupt the prayer camps.

"Water Protecters are calling on EVERYONE to check-in at Standing Rock, ND to overwhelm and confuse them.

"This is concrete action that we can do without leaving our homes that protect people who are putting their body and well-being on the line. Will you join me in Standing Rock?" the post from the Stand Against Dakota Access Pipeline- No DAPL Facebook page stated.

According to The Washington Post, protesters are unsure where the idea came from, but at least one of the major protest camps supports it. A spokesman for the Sacred Stone Camp told The Intersect that the viral post did not come from them, but they believe it is drumming up attention for their cause.

"We support the tactic, and think it is a great way to express solidarity," the spokesman said. "It looks like the copy and paste technique has created a unique way of generating numbers of support—it's more impactful to see thousands of our friends take the time to create a unique status update."

The Morton County Sheriff's Department has been using Facebook check-ins to find out who is at Standing Rock in order to target them in attempts to disrupt the prayer camps. Water Protecters are calling on EVERYONE to check-in at Standing Rock, ND to overwhelm and confuse them. This is concrete action that we can do without leaving our homes that can protect people who are putting their body and well-being on the line. Will you join me in Standing Rock?

The Sacred Stone Camp representative, however, noted that there are several protest camps and that none of those camps has the authority to speak for all organisers. The Washington Post reported that the Standing Rock Sioux Tribe has yet to comment on the idea through its official Facebook page, but several activist pages have shared the post.

Meanwhile, the Morton County Sheriff's Department said it does not track "Facebook check-ins for the protest camp or any location," adding the idea that it would participate in such an activity as "absolutely false".

Protesters have spent months trying to block the 1,172-mile (1,890 km) pipeline being built by a group of companies led by Energy Transfer Partners, L.P. The pipeline would provide the fastest and most direct route to transfer Bakken shale oil to refineries in the US Gulf Coast.

Supporters of the DAP argue that the pipeline would be safer than transporting oil by road or rail. However, the Standing Rock Sioux Tribe and environmental activists claim it threatens to contaminate the local water supply as well as sacred tribal sites in the area.