New protests have erupted against the construction of a controversial oil pipeline in the US state of North Dakota, which has angered Native Americans and environmentalists.

Protesters in Morton County, North Dakota, and Annapolis Harbor, Maryland, held fresh demonstrations Saturday, one day after 40 people were arrested at the construction site.

About 500 demonstrators briefly blocked two entrances to a pipeline work yard in Morton County, forcing workers to leave the area.

“They went west for a few miles (from there), they turned on that road that leads to the Mandan landfill and that’s where the North Dakota pipeline have equipment,” Morton County Sheriff’s Department spokesman Rob Keller said. “It’s their work yard.”

Keller said one protester was injured, but no one was arrested.

More than 300 Maryland protesters also marched alongside Native American residents Saturday to show their support for the Standing Rock Sioux Tribe of North Dakota.

The pipeline has infuriated the tribe and environmental activists who say it threatens the region’s water supply and sacred tribal sites. The tribe’s reservation is close to the pipeline's route.

Pipes being stacked for the Dakota Access oil pipeline last year at a staging site in Worthing, S.D. (Photo by AP)

The demonstrators chanted, "Mni Wiconi, Water is life" and "You can't drink oil! Keep it in the soil!"

"You have to stand for the Native," said marcher Barry Wilson of Charles County. "Like everything else, if you don't stick together and do what's right, the politicians will continue to do what they were going to do."

According to an administration official, who talked to POLITICO on Friday, "the process is ongoing and no decisions have been made."

The protests against the pipeline construction have spread to other cities across the United States, with other tribes, environmentalists and advocates for Native Americans joining the movement.

The federal government has twice requested the pipeline operator to voluntarily stop construction near the tribe's reservation while the project's route is being reconsidered by the authorities, however, courts have refused to order a halt.