BISMARCK, N.D. (AP) — North Dakota regulators signaled Thursday that the state would not impose conditions beyond those required by the federal government on a proposal to double the capacity of the Dakota Access Pipeline.

Zachary Pelham, an attorney for the three-member, all-Republican North Dakota Public Service Commission told the panel that requiring additional measures could be considered “outside our lane” and “potentially problematic,” drawing a legal challenge from Texas-based Energy Transfer, the pipeline’s owner.

The company wants to double the capacity of the pipeline to as much as 1.1 million barrels daily to meet growing demand for oil from North Dakota. It’s seeking permission for additional pump stations in the Dakotas, Iowa and Illinois.

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Commissioners in a South Dakota county last year approved a conditional use permit for a pumping station. Permits in the other states are pending.

Iowa regulators last week said the company must provide expert analysis to back up its claim that doubling the line’s capacity won’t increase the likelihood of a spill. On Tuesday, opponents of the expansion said the Illinois Commerce Commission voted to require the company to provide justification that the additional capacity is needed, including identifying shippers and contracts. The commission did not return telephone calls Thursday to confirm the action.

The pipeline has been moving North Dakota oil through South Dakota and Iowa to a shipping point in Illinois since June 2017.

The $3.8 billion pipeline was subject to prolonged protests and hundreds of arrests during its construction in North Dakota in late 2016 and early 2017 because it crosses beneath the Missouri River, just north of the Standing Rock Sioux Reservation. The tribe draws its water from the river and fears pollution. Energy Transfer insists the pipeline and its expansion are safe.

Tribal members are asking North Dakota regulators to deny the expansion, saying it would “increase both the likelihood and severity of spill incidents.” The tribe wants North Dakota regulators to seek a similar analysis to that sought by regulators in Iowa and Illinois.

“The North Dakota PSC has the statutory duty to determine whether the expansion has a minimum adverse impact on the state and citizens of North Dakota,” Tim Purdon, an attorney for the Standing Rock Sioux Tribe, said. “I don’t know how you can evaluate this without it.”

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PSC Commissioner Julie Fedorchak said in an interview the tribe’s concerns were addressed at a more than 15-hour meeting in November and also are addressed by the federal Pipeline Hazardous Materials Safety Administration.

The company has said that its $40 million pump station built on a 23-acre (9-hectare) site near Linton would produce only “minimal adverse effects on the environment and the citizens of North Dakota.” It says the expansion would lessen the need for additional pipelines or rail shipments from North Dakota, the nation’s second-biggest oil producer behind Texas.