The North Dakota Highway Patrol says a large group of Dakota Access protesters has caused the state Capitol in Bismarck to be locked down.

Highway Patrol Lt. Tom Iverson says a "large number of protesters" had gathered outside the building Monday morning. He says the Capitol was locked to avoid them gathering inside the building. The patrol is in charge of Capitol security.

Several troopers were patrolling the Capitol and the grounds.

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Earlier this month, more than a dozen protesters were arrested in the judicial wing of the Capitol in Bismarck. Highway Patrol Lt. Tom Iverson said the protesters were sitting, chanting and singing and refused orders to leave. Three other people who refused orders to leave the governor's residence on the Capitol grounds were also arrested