SEATTLE (AP) — Federal authorities in Seattle have charged two people with a terrorist attack on train tracks, suggesting they were motivated by opposition to the construction of a natural gas pipeline across British Columbia when they interfered with the operation of a railroad in Washington state.

Samantha Frances Brooks, 27, and Ellen Brennan Reiche, 23, both of Bellingham, are accused of placing “shunts” on Burlington Northern Santa Fe tracks Saturday night. Such devices consist of a wire strung across the tracks, mimicking the electrical signal of a train. The devices can cause trains to automatically brake and can disable railroad crossing guards, investigators said in a complaint filed Monday.

The pair are charged only in Saturday night's incident, but there have been 41 such cases involving the BNSF tracks since January, with a message claiming responsibility posted on an anarchist website early this year, the FBI's Joint Terrorism Task Force said.

In one, shunts were placed in three locations in northwest Washington on Oct. 11, prompting emergency brakes to engage on a train that was hauling hazardous materials and flammable gas. The braking caused a bar connecting the train's cars to fail; the cars became separated and could have derailed, U.S. Attorney Brian Moran said in a news release.

“These crimes endanger our community," Moran said.

Brooks and Reiche were arrested after triggering a game camera on BNSF property, the complaint said. They made an initial court appearance Monday and were released pending a Dec. 14 hearing. Their attorneys declined to comment Monday afternoon.

The charge carries a prison term of up to 20 years.

Opponents say the 416-mile (670-km) Coastal GasLink Pipeline Project would worsen environmental damage and infringe on the rights of First Nations people in British Columbia. The message claiming responsibility for the shunts said the goal was to keep supplies from reaching the U.S.-Canada border.

“This tactic is fast and discreet,” the message said. “On a single rail track with a Centralized Traffic Control (CTC) system, this simple action can generate enough confusion in the system to cause big slow downs and bureaucratic delays.”

TC Energy, the Alberta company behind the pipeline proposal, has said it is committed to partnering with the 20 First Nations that have executed agreements related to the project and has provided them an opportunity to invest in it.