Fifty-five Keystone XL Pipeline protesters were arrested after storming an office lobby in Washington Friday afternoon.
The protesters targeted offices of Environmental Resources Management in the 1700 block of I Street NW, a consulting firm hired to assess the proposed pipeline's environmental impact.
Police say management asked the protesters to leave, but they refused.
The Keystone XL Pipeline is a proposed 1,179-mile crude oil pipeline, beginning in Canada and extending south to Texas.
Some reports say the pipeline would have no significant environmental impact to most resources along the proposed route.
Republicans and business and labor groups have urged the Obama administration to approve the project as a source for jobs and a step toward North American energy independence.
But environmentalists see the State Department report in a vastly different light, saying it would carry "dirty oil" that contributes to global warming. They also worry about a spill.