Protesters against the Dakota Access Pipeline at Standing Rock, North Dakota, believe the local Morton County sheriff’s department is monitoring Facebook “check-ins” at the Indian reservation to get a sense of who’s protesting. And someone’s apparently trying to mess with that monitoring.

A call went out for Facebook users over the weekend to falsely check in at Standing Rock to confuse the police regarding protester identities and numbers. But it isn’t clear whether the directive came from organizers on the ground at the Camp of the Sacred Stone, who call themselves Water Protectors because of the purported threat that the planned pipeline poses to Standing Rock’s water supply, or whether it’s a hoax.

Hoax or not, the social media campaign had gone viral by Monday. Keshia Pendigrast, a student and staff member at the Union Theological Seminary in New York, said she had more than 65 friends check in at Standing Rock on Monday morning alone. After investigating further, she decided to add her name. “I think we underestimate how often Facebook is used by law enforcement,” Pendigrast said. “So if my small check-in confuses a sheriff somewhere, I’m happy.”

Protesters have been camped out at Standing Rock since April in response to the planned Energy Transfers Pipeline, but tensions reached a boiling point last week when protesters clashed with police and several vehicles were set on fire. Scenes of standoffs between riot police and protesters linked arm-in-arm were broadcast online via Facebook Live. Law enforcement used a sound cannon in an attempt to disperse protesters.

The unrest spilled over into the following days. On Saturday alone, over 100 protesters were arrested.

By September, there were an estimated 4,000 protesters in the camp, NBC News reported, quoting Standing Rock Sioux Chairman Dave Archambault II, and several thousand more on the weekends. There were also representatives from 300 federally recognized tribes.

Morton Sheriff’s Department did not respond to VICE News’ request for comment.