ST. PAUL -- PolyMet has formally applied for a permit to build a copper-nickel mine in northeastern Minnesota.

The application is a key step in the process to build the mine near Babbitt, and now triggers an extended review of the company's finances and the project's potential environmental impact.

In March, the Department of Natural Resources approved the project's final environmental review, which paved the way for this permit application. The DNR says the permit review will take months.

The mine has been controversial.

Supporters say it would bring new jobs to northeastern Minnesota. But environmental groups and local Indian tribes have criticized the DNR's environmental analysis, and worry that approving PolyMet could lead to other proposed mines in the region