The Dakota Access Pipeline started shipping oil on Thursday to contractors between North Dakota and Illinois, the Associated Press reported.

The pipeline's developer, Energy Transfer Partners, successfully completed building the $3.8 billion pipeline in mid-May. The pipeline, which stretches 1,172 miles long, is expected to carry 570,000 barrels of oil a day. The Dakota Pipeline has partnered with the Illinois-to-Texas Energy Transfer Crude Oil Pipeline, and already has a commitment of 520,000 barrels per day from shippers.

Although the pipeline has started shipping, it is expected to face scrutiny this summer. The AP reported that "North Dakota's Public Service Commission is looking into whether Texas-based Energy Transfer Partners removed too many trees and shrubs, and whether it improperly reported the discovery of Native American artifacts."

ETP said it has not intentionally done anything wrong, but the company could face tens of thousands in fines if regulators decide otherwise.

The pipeline took years to complete and has faced backlash from former President Barack Obama and environmental activists. Thousands of protestors last year flooded Standing Rock Sioux reservation in North Dakota in an attempt to delay the project. Their attempts failed and the environmentalists left the site, leaving behind large quantities of trash.

Obama halted the project in December by refusing to grant the Army Corps of Engineers an easement to route the pipeline below Lake Oahe, which is near the reservation.

President Donald Trump approved the grant after taking office.