Protests against the construction of the Dakota Access pipeline are endangering the safety of the public and violating federal aviation rules, authorities said.

Companies led by Energy Transfer Partners are building the 1,100-mile pipeline meant to carry oil from North Dakota to refineries along the southern U.S. coast. The Standing Rock Sioux tribe and its supporters have tried to block the construction through the courts and through protests, saying the pipeline would threaten tribal sites and regional water supplies.

More than 80 protesters were arrested Saturday by officers from the Morton County Sheriff's Department, who used pepper spray on pipeline demonstrators. On Sunday, the sheriff's office said protestors used an unmanned aircraft system to harass a surveillance helicopter, established an illegal road block and occupied private property during their protests near a pipeline construction site.

North Dakota sheriffs said protests were neither lawful nor peaceful. The Standing Rock Sioux tribe countered that law enforcement officials beat area demonstrators and using a "militarized" response to quell the protests.

County officials coordinated a visit to the construction site last week. Parties to the visit included state archeologists and representatives from the Standing Rock Sioux tribe. Morton County Sheriff Kyle Kirchmeier said in a statement the visit was constructive and all parties were working to better understand each other's position.

The partnership behind the pipeline said it's needed to accommodate and distribute the amount of crude oil being produced from the Bakken shale oil basin in North Dakota. Rail takes away some of the oil from North Dakota, a transport method that has its own public safety risks. At least 40 people were killed in Lac-Megantic, Quebec, in the 2013 derailment of a train carrying tankers of crude oil from North Dakota to Canadian refineries.