CANNON BALL, North Dakota — Authorities removed all remaining Dakota Access Pipeline protesters from their camp on Thursday.

The final search of the Oceti Sakowin camp — which over the last months has hosted thousands of protesters trying to block construction of the oil pipeline — took about 3 1/2 hours and resulted in about three dozen arrests, the Associated Press reported.

Hundreds of demonstrators on Wednesday at the encampment near the Standing Rock Sioux reservation had been given a deadline to leave the area or face arrest. As the deadline approached, some protesters were seen leaving the area, and a handful of wooden structures used by the demonstrators were set on fire.

An executive evacuation order signed by North Dakota Governor Doug Burgum on Feb. 15 said the encampment would be closed down due to flooding concerns from melting snow in the area.

Burgum’s order said “accumulated debris, including human waste generated by the populations that have occupied the aforementioned areas of Morton and Sioux Counties pose a significant and increasing environmental threat” to the area.