Four protesters were in custody Monday afternoon in Itasca County after tampering with equipment along Enbridge's oil pipeline corridor across northern Minnesota.

The pipeline protesters, who call themselves the Four Necessity Valve Turners, posted a video to their Facebook page showing their actions to close valves on Enbridge's pipelines at noontime Monday.

Itasca County Sheriff Vic Williams said four people were in custody in connection with the incident. The county jail said it is holding Daniel Yildirim, 32, of Viroqua, Wis., on suspicion of trespassing.

"We are in the very early stages of the investigation," he said. Williams said he isn't sure if the protesters actually shut down the oil flow.

The group in a statement said it turned off the valves of three of the pipelines. Besides Yildirim, the group said the other participants were Michele Naar Obed of Duluth, Allyson Polman of Texas and Brenna Cussen Anglada of Wisconsin.

Diane Leutgeb Munson, a spokeswoman for the group, said it was her understanding that the protesters contacted Enbridge before turning the valves for safety reasons and "to give Enbridge the opportunity to turn it off themselves."

The protesters claimed on their Facebook page that Enbridge's Line 4 had been off for 45 minutes.

Enbridge declined to confirm that any of its pipelines were shut down. In a statement, the Calgary, Alberta-based company said: "The actions taken to trespass on our facility and tamper with energy infrastructure were reckless and dangerous."

Neither Enbridge nor the Itasca County Sheriff's Office disclosed the location of the incident. The protesters' statement said it was in Blackberry Township.

Enbridge runs six pipelines across northern Minnesota to its terminal in Superior, Wis., the largest conduit of Canadian oil into the United States. The company's $2.6 billion plan to replace its current Line 3 in Minnesota with a new pipeline has been highly controversial.

The Four Necessity Valve Turners described themselves on their Facebook page as a group in the tradition of the Catholic Worker movement that is taking a stand against the "climate crisis" brought on by oil use.

"Each [of us] feel personally called to step into responsibility by standing in the way of this deadly fossil fuel industry, which benefits the few at the expense of all life, especially those who are the most vulnerable," they said in a letter posted on the site.

Enbridge, in its statement, said: "The people involved [in the incident on Monday] claimed to be protecting the environment, but they did the opposite. Their actions put themselves, first responders, neighboring communities and land owners at risk."

In October 2016, Seattle-based activists broke into Enbridge property about 35 miles northwest of Bemidji and turned valves on two pipelines.

In that case, too, the protesters informed Enbridge ahead of time and videotaped themselves.

Three of them were charged with felony property damage. But the charges were thrown out last October by Clearwater County District Judge Robert Tiffany, who ruled there was not enough evidence to prove property damage.

The Minnesota Public Utilities Commission approved Enbridge's new Line 3 in June, though the company must still get several state and federal environmental permits.

Enbridge plans to get construction going this spring in time to finish the pipeline by November.

The current Line 3, built in the 1960s, is corroding and can be operated at only 51 percent of capacity for safety reasons. Enbridge said the new pipeline, which will partly follow a new route, is a necessary safety upgrade and will restore the full flow of oil on Line 3.

Environmental groups and some Ojibwe bands have opposed the new pipeline, saying it would exacerbate climate change and open up a new region of Minnesota's lakes, rivers and wetlands to possible environmental damage from oil spills.