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BALL, N.D. (AP) — The Federal Aviation Administration is restricting flights over an area of North Dakota where law enforcement and people protesting the construction of the Dakota Access oil pipeline are bracing for a confrontation.

The restriction went into effect Wednesday and will last until Nov. 5.

Authorities say only aircraft affiliated with the North Dakota Tactical Operation Center are allowed within a radius of about 4 ½ miles of Cannon Ball, where the protesters have set up camp. The FAA has also banned drones in the airspace.

A months-long dispute over the pipeline reached a crisis point at the weekend when some 200 protesters set up camp on land owned by pipeline developer Energy Transfer Partners. On Wednesday, authorities gathered in the area with heavy equipment including Humvees and buses and demanded they leave. The protesters refused.