BISMARCK, N.D. (AP) — A United Nations official who visited North Dakota in the wake of months of protests over the disputed Dakota Access oil pipeline believes the concerns and rights of Native Americans haven't been adequately addressed.

North Dakota Republican Gov. Doug Burgum says the state has respected legal protests and that it focused on maintaining peace and protecting the environment. He said his administration is working to restore relations with the Standing Rock Sioux.

The tribe has led the fight against the $3.8 billion pipeline to move North Dakota oil to Illinois. The opposition became centered at a camp that protesters established on federal land between the tribe's reservation and the pipeline route. It grew at times to thousands of people, many of whom clashed with police, leading to about 750 arrests since August.

"My impression is that there was unnecessary use of force," Victoria Tauli-Corpuz, U.N. special rapporteur on the rights of indigenous peoples, told The Associated Press after visiting the area this week at the invitation of Standing Rock Sioux Chairman Dave Archambault. "Anybody has a right to protest and express their opposition to what is happening."

Police say some protesters were violent and took part in riots, and that some targeted police both professionally and personally.

"Through this ordeal, our law enforcement personnel have shown great professionalism and restraint as they faced taunts, verbal abuse, threats, thrown objects and even gunshots," Burgum told the AP.

The main protest camp recently was shut down in advance of spring flooding, and a federal contractor is cleaning up hundreds of tons of trash and debris before it can pollute nearby rivers. Tauli-Corpuz acknowledged the large amount of garbage but said she considered it "not such a huge issue."

"Efforts to clean it up could be undertaken even if people were there," she said.

Burgum said the pollution concern and the cleanup that could cost federal taxpayers up to $1.2 million isn't overblown.

"More than 600 truckloads of garbage, building materials and toxic debris were hauled away from the protest camps. ... Most North Dakotans would agree that's 'a huge issue,' " he said.

Tauli-Corpuz also said she believes the tribe wasn't properly consulted about the pipeline route — an argument the tribe has made in a federal lawsuit against the Army Corps of Engineers and Texas-based pipeline developer Energy Transfer Partners. The defendants dispute that claim.

The tribe says the pipeline threatens its water, sacred sites and religion. The tribe successfully pushed for a full environmental study of the pipeline's crossing under Lake Oahe, a Missouri River reservoir from which it draws water. However, the Corps rescinded the study at the urging of President Donald Trump.

Tauli-Corpuz said she's likely to recommend a full environmental study in a September report to the U.N. Human Rights Council. The report will have no force of law.

She isn't the first U.N. official to weigh in on the pipeline. The U.N. Permanent Forum on Indigenous Issues last August issued a statement calling for more tribal input. Forum member Edward John visited the camp in late October, saying he found a "war zone" atmosphere, and the group issued a statement in November calling on the U.S. government to protect sacred sites and uphold human rights.

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