(CNN) In a surprise reversal, the Environmental Protection Agency announced it is withdrawing its plan to suspend environmental protections for an area of Alaska that is home to the world's most valuable wild salmon fishery.

The EPA proposed last year to "reverse clean water safeguards" for the Bristol Bay watershed, paving the way for a massive gold and copper mine to be built in the region.

The controversial proposal would have canceled an EPA protection put in place during the Obama administration. After years of study, the EPA found in 2014 that a mine "would result in complete loss of fish habitat" in some areas of the bay, and that "all of these losses would be irreversible."

The Bristol Bay watershed is one of the most pristine ecosystems in the world, supplying about half of the world's sockeye salmon.

A CNN investigation last fall found that EPA Administrator Scott Pruitt ordered his staff to reverse the environmental protection within hours after meeting with the CEO of the mining company, Pebble Limited Partnership. Shortly after CNN's report, more than 40 congressional Democrats wrote a letter expressing "deep concern" about the EPA's reversal.

"I found out from your story that they actually had an agreement," Sen. Maria Cantwell of Washington state told CNN's Anderson Cooper. "Doing a sweetheart deal for a mining executive, five minutes after he leaves your office, is not the due process that taxpayers want."

Alaska governor Bill Walker had also spoken to Pruitt about his opposition to the mine several times over the past year.

"I have shared with him my belief that in the Bristol Bay region we should prioritize the resource that has sustained generations and must continue to do so in perpetuity," Walker said in a news release. In his state of the state address, Walker noted that the Bristol Bay fishery celebrated the harvest of its two billionth salmon last year.

In the EPA's latest decision, released late Friday, Pruitt wrote, "it is my judgment at this time that any mining projects in the region likely pose a risk to the abundant natural resources that exist there. Until we know the full extent of that risk, those natural resources and world-class fisheries deserve the utmost protection."

The EPA will continue to take public comment on the mine, and its announcement means the plan to withdraw the environmental protections is on hold while the EPA "receives more information on the potential mine's impact on the region's world-class fisheries and natural resources." a

Last year, the EPA and Pebble Limited Partnership reached a settlement agreement that allowed the mining company to apply for a permit. While Friday's decision still allows a pathway for the Pebble Mine to be developed, the EPA statement says any permits to build "must clear a high bar, because EPA believes the risk to Bristol Bay may be unacceptable."

The mining company says its application for a permit remains on track.

"We have every confidence that Pebble's ultimate project design will meet the rigorous environmental standards enforced in Alaska and the US," said Ron Thiessen, president and CEO of Northern Dynasty, Pebble's parent company in a statement. He said the permitting process "will demonstrate that compliance through an open, objective, transparent and science-driven review."