Protests against the construction of an Enbridge oil pipeline in Minnesota continued for a second day after about 200 people were arrested.

The Canadian pipeline giant evacuated 44 workers on Monday after more than a thousand people descended onto two work sites, including a pump station and another location along the Mississippi River. The groups are seeking to stop construction of the company’s controversial Line 3 oil sands conduit, which they say is a threat to indigenous land and the environment.

“There are some people floating in again,” Cory Aukes, Hubbard County sheriff, said by phone. “Sounds like the protests have rekindedled.”

Producers in the Canadian oil sands, the world’s third-largest crude reserves, have struggled to ship their output to refineries in the US and abroad due to a shortage of export pipelines. But efforts to build new ones have faced fierce opposition. In January, President Joe Biden canceled a permit to build TC Energy’s Keystone XL pipeline, forcing the company to stop work that had already begun.

Indigenous groups and local communities have expressed concern about the impact to their land and waters.

Enbridge didn’t immediately return an email seeking comment.

Work on Line 3, which is schedule to enter operation this year, was still being impeded on Tuesday after about 200 people spent the night at a location where the pipeline would cross the Mississippi River, Big Wind, a member of the Northern Arapaho Nation and the Giniw Collective, said by phone.

Protesters had also chained themselves to equipment at the pump station and some were still at that site after spending the night there. Activists there, who had clashed with law enforcement officers on Monday, included actress Jane Fonda, Big Wind said.

At one point on Monday, a US Customs and Border Protection helicopter hovered low over the protesters at the pump station, kicking up dust, according to the Facebook page of the Northern Lights Task Force, a group of law enforcement agencies handling the Line 3 protests.

The coalition of indigenous and environmental protesters are asking the Biden Administration to intervene and stop Line 3’s construction, Big Wind said. Otherwise, the protesters are prepared to hunker down and keep blocking Enbridge’s work, just as indigenous groups in the Standing Rock Sioux Reservation did several years ago, delaying completing of the Dakota Access Pipeline.

“The administration doesn’t want another Standing Rock to happen, but if they don’t stop this line, they are going to get another Standing Rock,” he said.