The company behind the Dakota Access Pipeline continued to move drilling equipment into place near the Missouri River Monday, the day after police used water cannons, tear gas, and rubber bullets to disperse protesters in freezing temperatures.

For the last week, the company has been preparing to drill under Lake Oahe, a reservoir behind a dam on the Missouri River, though it doesn’t yet have an easement it needs from the Army Corps of Engineers to begin. “All activity is taking place on private land for which we have all the necessary permits and approvals,” Energy Transfer Partners spokesperson Vicki Granado told VICE News.

The government agency has jurisdiction over Lake Oahe and a spokesperson for the Army Corps of Engineers said the pipeline company can drill for 200 feet before hitting federal land. If it goes any further, the government will take enforcement action.

Protesters fear the Dakota Access Pipeline will leak crude oil into their water supply if it’s built under Lake Oahe, and as construction creeps closer to the lake, tensions have escalated.

Violence erupted Sunday night as protesters confronted police at Blackwater Bridge on Highway 1806 in a melee that resulted in 167 injuries, according to the Indigenous Environmental Network. On Monday, about 200 protesters rallied in Bismarck, North Dakota to call on President Barack Obama to condemn Sunday night’s police crackdown. The Bismarck protest was smaller than the thousands of people, by some estimates, who occupy the main protest camp.

Amnesty International announced Monday it had sent another delegation of human rights observers to monitor the protest — the fourth time since August they had done so. In a letter to the Morton County Sheriff’s Department, the group called Sunday night’s reports “alarming.”

“The type of equipment used to disperse an assembly must be carefully considered and used only when necessary, proportional and lawful. Policing and security equipment – such as rubber bullets, tear gas and stun grenades, often described as “less-lethal” weapons – can result in serious injury and even death,” the Amnesty International letter reads.

Protester Conor Handley said the conflict began when the demonstrators tried to remove two burned out vehicles that were blocking the road. However, police say the conflict started when protesters lit fires, so they used the water cannons to put them out.

“They really escalated things really quick,” Handley said of police.

Handley said he saw several people hit with rubber bullets, including people who were hit in the face. As he took photos up close of what was happening, he was hit with a water cannon in the back. The water froze quickly, coating his back in ice.

On Monday, Energy Transfer Partners, the company behind the pipeline project, continued to prep its drill pad near the Missouri River, even though the Army Corps of Engineers hasn’t yet granted a easement allowing the company to drill under the lake.

“It’s outrageous,” Handley told VICE News from Bismarck. “The Army Corps of Engineers has asked them to stop what’s going on, to stop drilling, and they’re slowly preparing to go forward anyway, to ignore federal orders.”

The Army Corps of Engineers says it wants to discuss the issue further with the Standing Rock Sioux Tribe before deciding whether to grant the easement, “in light of the history of the Great Sioux Nation’s dispossession of lands, the importance of Lake Oahe to the Tribe, our government-to-government relationship and the statute governing easements through government property.”

But the company behind the Dakota Access Pipeline doesn’t want to wait. On Nov. 15, Energy Transfer Partners and Sunoco Logistics Partners filed applications in U.S. federal court seeking a judgement declaring that Dakota Access Pipeline has the legal right of way to build, complete and operate the pipeline without any action from the Army Corps of Engineers. If granted, it would remove the need for the easement.

Granado said there is no timeline for the ruling, “however it is our hope that the judge will act expeditiously.”