HELENA, Mont. — State environmental regulators are asking the developers of a proposed underground copper mine in central Montana for more information before they begin working on an environmental impact statement.

The Department of Environmental Quality on Thursday asked Tintina Montana Inc. how it plans to plug mine shafts after they’re closed to prevent water from being released.

The DEQ also asked Tintina to complete its air quality, public water supply and surface water discharge permit applications and to clarify a few more pieces of information.

Tintina initially applied for a mining permit near White Sulphur Springs in December 2015. This is the third time the DEQ has requested more information.

When the application is complete, DEQ will prepare an environmental impact statement and gather public comment.

Environmental groups worry the mine could damage water quality in the area.