Five oil pipelines disrupted by environmental protesters were back up and running on Wednesday, although at least one of the lines that carry millions of barrels of crude from Canada to the United States was operating at reduced rates.

In an unprecedented coordinated attack on Tuesday, protesters broke into valve stations at five remote locations to stop the flow of crude through arteries that pump around 15 percent of the oil consumed in the United States every day.

Companies operating the pipelines shut down their lines for between five and seven hours as a safety measure before the restart, according to Reuters estimates and company representatives.

The action on Tuesday underscored the vulnerability of the thousands of miles of pipeline in the United States that deliver energy to consumers.

Together, the pipelines have the ability to carry nearly 2.8 million barrels a day of crude across the Canadian-U.S. border.

In Washington, White House spokesman Josh Earnest said on Wednesday the departments of Homeland Security and Transportation were “trying to get to the bottom of what exactly happened and what potential steps could be taken to ensure the safety and security of our energy infrastructure.”

“We certainly take that security quite seriously,” Earnest told a daily news briefing.

Protest group Climate Direct Action said on Tuesday the action was to support the Standing Rock Sioux Tribe, which is protesting construction of the $3.7 billion Dakota Access pipeline, carrying oil from North Dakota to the U.S. Gulf Coast.

Activists across Montana, Minnesota, North Dakota and Washington state were arrested on Tuesday after the early-morning raids, which they posted on social media.

TransCanada Corp’s Keystone pipeline, Spectra Energy Partners LP’s Express pipeline and Enbridge Inc’s Line 4 and 67 all restarted Tuesday afternoon, according to company representatives.

Information provider Genscape said Keystone was running at reduced rates.

Kinder Morgan Inc said it was not operating the spur of the pipeline affected by the protesters, although it has since restarted the rest of the pipeline.

In Texas on Wednesday, a separate group of activists planned a gathering in front of the offices of Energy Transfer Partners, spearheading construction of Dakota Access, to protest the pipeline.

Source: www.reuters.com