The US Army Corps of Engineers has allowed the Dakota Access Pipeline to continue construction under the Missouri River, threatening the water supply of an indigenous community, shortly after the President signed an executive order.

Vicki Granado, spokeswoman for Energy Transfer Partners, the parent firm of the company building the 1,172-mile pipeline, said work would start "immediately".

The company added that the pipeline would be in service within about 83 days - less than three months. Company Dakota Access can now dig the pipe through four states, including under Lake Oahe and through government land in North Dakota, affecting the water of the tribe and 17 million people who live downstream.

The Standing Rock Sioux Tribe has long opposed the project, which they say would also destroy their historical artifacts and way of life, said it would launch a legal fight, but also admitted they were running out of legal options.

The tribe will argue that the environmental impact statement process was wrongfully terminated.

The dramatic turnaround comes two weeks after President Donald Trump signed an executive action to urge a review of the pipeline and other energy projects, dismissing former President Barack Obama’s efforts to block them.

"Let’s get this pipeline built," he said.

What is the Dakota Access Pipeline?

The pipeline is set to cost $3.7 billion, and the developer said it would bring $156 million in sales and income taxes to local and state governments, and would provide up to 12,000 construction jobs.

In November former President Obama ordered the Army to consider re-routing the pipeline to avoid being built within half a mile of an indigenous community.

The Standing Rock Sioux Tribe, along with other campaigners and thousands of military veterans, engaged in peaceful marches to block the pipeline construction, even in freezing temperatures and snow blizzards.

Trump signs executive orders to advance oil pipelines

Law enforcement allegedly used water cannons and even a grenade to break up the group, prompting rage from civil rights groups. There were almost 700 arrests. One woman campaigner’s arm was severely damaged when it was hit by a police canister, prompting a Department of Justice investigation.

Tom Goldtooth, Native American environmental activist, told The Independent that the protests would now be repeated, as their plight had gained sympathy from around the world.

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The Army Corps had started a new study of the pipeline and its impact on 18 January, two days before Mr Obama left the White House, which would have taken up to two years to complete. Energy Transfer Partners responded that the review was politically motivated.

ETP has already drilled entry and exit holes for the crossing by Lake Oahe, and oil has been put in the pipeline leading up to the lake as the company anticipates finishing the project.

Six days later, new President Trump signed an order, demanding the Corps review Mr Obama's study. He also eased progress for TransCanada to push ahead with its controversial project, the $8 billion Keystone XL pipeline which would run 1,200 miles across six states, shifting petroleum from Canada to the Gulf Coast.