Market Street reopened late Tuesday morning after activists opposing the Dakota Access Pipeline gathered in Civic Center Plaza before marching along Market Street and blocking a U.S. Army Corps of Engineers building in San Francisco.

A large group gathered at sunrise in the plaza outside of City Hall in protest of the proposed North Dakota pipeline that opponents say could pollute drinking water, including on land occupied by the Standing Rock Sioux tribe.

The activists then marched to the Army Corps of Engineers’ San Francisco district headquarters at 1455 Market St. between 10th and 11th streets. Some protesters stood in the middle of Market Street, blocking traffic, while others blocked the doorway to the building.

The protest was organized by groups including Diablo Rising Tide and Idle No More SF Bay and is part of a nationwide day of action against the pipeline, according to Idle No More organizer Isabella Zizi.

“We are not protesters, we are water protectors,” Zizi said.

She said the actions in recent weeks at the site of the proposed pipeline and elsewhere around the nation have had an impact, pointing to a statement released by the Army Corps of Engineers on Monday saying the project needs further analysis and discussion before going forward.

“The Army invites the Standing Rock Sioux Tribe to engage in discussion regarding potential conditions on an easement for the pipeline crossing that would reduce the risk of a spill or rupture, hasten detection and response to any possible spill, or otherwise enhance the protection of … the Tribe’s water supplies,” the agency’s statement said.

Zizi said she wasn’t worried about the impact that the election of Donald Trump as the next U.S. president might have on the project.

“I know the thousands of people I am with today will stand together and support one another,” she said.

The group began marching back to Civic Center Plaza shortly before 11 a.m. No arrests have been reported.

San Francisco Municipal Railway officials said Muni routes that cross or operate on Market Street have been rerouted or turned around as a result of the demonstration.

UPDATE: All Market St lines are stopped due to protest. Allow extra time and try to find alternate routes due to police activity.

— SFMTA (@sfmta_muni) November 15, 2016

#NoDAPL protesters sitting on Market Street to protest oil pipeline pic.twitter.com/OE8TFxA4PL

— Blue Marble Love (@LoveBlueMarble) November 15, 2016

Fed great to be in the streets with #NoDAPL indigenous-led protest–no more sound system just drums and voices. Blocking Market Street! pic.twitter.com/4Z2Dshjk2b

— Cleo Wolfki (@technodowser) November 15, 2016

Fed great to be in the streets with #NoDAPL indigenous-led protest–no more sound system just drums and voices. Blocking Market Street! pic.twitter.com/4Z2Dshjk2b

— Cleo Wolfki (@technodowser) November 15, 2016