CANNON BALL, North Dakota - It's unlikely all the people Facebook users see check in at Standing Rock Indian Reservation are actually there; instead, they're part of a social media force in an on-going fight over a pipeline.

Hundreds of thousands of people have checked in - a Facebook feature allowing users to post their location - at the reservation. Demonstrators are protesting a pipeline that will span four states. The $3.7 billion project will connect oil deposits in North Dakota to Illinois where it could be shipped more easily to refineries along the Gulf Coast. Supporters believe the pipeline will lessen the United States' dependence on foreign oil. Activists, though, argue the project will harm the environment and destroy Native American cultural sites.

Those who have gathered to protest the pipeline believe law enforcement are monitoring Facebook check-ins to track them and asked people from other areas to check in there to "overwhelm and confuse" law enforcement. The local sheriff's office said no such social media monitoring is happening.

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