By Stephanie Keith

MANDAN, N.D. (Reuters) – A decision on whether the Dakota Access Pipeline will be allowed to tunnel under a lake near sacred tribal lands in North Dakota will come in the next few days, possibly by Monday, a U.S. government spokeswoman said on Friday.

The statement by spokeswoman Amy Gaskill of the U.S. Army Corps of Engineers came as police again confronted protesters at a construction site on the controversial pipeline, which has drawn steady opposition from Native American and environmental activists since the summer.

At least 39 protesters were arrested on Friday at the construction site, and deputies took pictures of vandalized equipment, which had wires cut and was spray-painted, Morton County Sheriff’s Department spokeswoman Donnell Preskey said.

She said police confronted about 100 protesters at the scene.

Smoke was seen billowing from a large excavation machine near a site off Route 6 in rural North Dakota, and protesters had also climbed into other equipment, according to a Reuters witness. Two workers were seen leaving the scene.

Completion of the $3.7 billion Dakota Access Pipeline, set to run 1,172 miles (1,885 km) from North Dakota to Illinois, was delayed in September so federal authorities could re-examine permits required by the Army Corps of Engineers.

Plans called for the pipeline to pass under a federally owned water source, Lake Oahe, and to skirt the Standing Rock Sioux Reservation by about a half-mile (one km). Most of the construction has been completed, save for this area under the lake.

The Standing Rock tribe and environmental activists said the project would threaten water supplies and sacred Native American sites and ultimately contribute to climate change.

The Obama administration requested a voluntary halt to construction within 20 miles of the lake on each side.

Energy Transfer Partners <ETP.N>, which owns the line, continued to build to the edge of the federal land where the lake is located.

The company earlier this week said it was “mobilizing” drilling equipment to prepare to tunnel under the lake. That has angered protesters, who planned more protests in coming days.

An ETP spokeswoman said, “Construction is actually complete in North Dakota, except for the bore under the lake, so there is nothing for them to stop.”

Pipeline supporters say the project offers the fastest and most direct route for bringing Bakken shale oil from North Dakota to U.S. Gulf Coast refineries and would be safer than transporting the oil by road or rail.

(Reporting by Stephanie Keith in Mandan, North Dakota; additional reporting by Liz Hampton in Houston and Steve Gorman in Los Angeles; Editing by Chizu Nomiyama and Cynthia Osterman)