NEW YORK (Reuters) - Construction equipment for Dakota Access LLC’s controversial $3.7 billion oil pipeline suffered about $2 million in damage in an intentionally set fire over the weekend in Iowa, authorities said on Monday.

The Jasper County Sheriff’s office said the fire occurred late Saturday near the town of Reasnor, Iowa, near where other equipment was set ablaze in August along the pipeline route, which is planned to carry oil from North Dakota to the U.S. Gulf Coast. State and federal authorities are investigating.

Dakota Access said in an emailed statement it “experienced the intentional burning of construction equipment by unknown individuals. These illegal actions have resulted in millions of dollars in damage.”

The Standing Rock Sioux tribe and environmental activists have been protesting construction of the 1,100-mile (1,886-km) pipeline in North Dakota for several months because they say it threatens water supply and sacred sites.

On Monday, dozens of demonstrators gathered outside the Morton County Courthouse in North Dakota to protest the pipeline and support for a journalist charged with rioting.

Construction of one section in North Dakota has been halted in response to the tribe’s concerns and is under federal review.

The company, a unit of Energy Transfer Partners LP ETP.N, on Monday offered a $100,000 reward for information leading to an arrest and conviction in the case, but it did not immediately respond to a request for details on the incident.

Opposition to pipeline construction has increased in recent years, with activists protesting against the Keystone XL line that was rejected by the Obama administration.

Last week, climate-change activists disrupted the flow of millions of barrels of crude from Canada to the United States in coordinated efforts that targeted several key pipelines simultaneously.

Protest group Climate Direct Action said the move was in support of the Standing Rock Sioux Tribe.

A North Dakota judge on Monday dropped misdemeanor rioting charges against Amy Goodman, a journalist from the TV and radio program “Democracy Now!,” said Goodman and her attorney, Tom Dickson.

McLean County State’s Attorney Ladd Erickson, who filed the complaint against Goodman, did not immediately respond to a request for comment.

Separate trespassing charges against Goodman were dropped on Friday, Dickson said.

Goodman said that the dismissal of charges was “a great vindication of the First Amendment.”

The charges stemmed from Goodman’s Sept. 3 report that showed security guards at the pipeline using dogs and pepper spray to subdue pipeline protesters.