A new report from the House Oversight Committee accuses the U.S. Environmental Protection Agency (EPA) of inappropriately blocking the Pebble Project in Alaska.

The report says the EPA knew its “preemptive veto” of the Pebble Bay project last year was “unprecedented,” that it blocked the mining permit before reviewing petitions on the matter and that it improperly worked on the permit denial with mining opponents, The Hill reported.

In a letter to the EPA, three committee Republicans write that the agency’s denial of the project was “highly questionable and lacking a legal basis.”

“The findings … show that EPA’s actions with respect to Pebble Mine are highly questionable and lacking a legal basis,” the members, led by Committee Chairman Jason Chaffetz (R-UT), write in their letter. The lawmakers ask the EPA to withdraw its denial decision and conduct a further review of the project instead.

The EPA moved to deny a permit for the Pebble Mine project last year, arguing it would threaten local wildlife and waterways. The agency has said it conducted three years of scientific evaluations and public hearings before deciding on the matter.

“EPA use of its authority has typically involved major projects with significant impacts on some of America's most ecologically valuable waters,” agency spokeswoman Monica Lee said in a statement.

“EPA Region 10's proposal to protect the Bristol Bay watershed outlines restrictions that would protect waters that support salmon in and near the Pebble deposit. These restrictions apply to impacts associated with large-scale mining of the Pebble deposit. No other lands or development are subject to the restrictions.”

The agency’s conclusions were echoed in a separate report from the Natural Resources Defense Council (NRDC), which defended the decision.

The group also questioned a study from William Cohen, a former secretary of Defense who investigated the issue for the Pebble Partnership, the firm behind the mine project. His report said the agency gave special treatment to opponents of the mine.

NRDC’s analysis said the EPA “actually carried out a methodical scientific review over a period of four years, highlighted by extraordinarily comprehensive public participation.”