MADISON, Wis. — The Wisconsin Department of Natural Resources wants more data from a company planning to open a huge iron mine in northwestern Wisconsin before approving bulk sampling activity.

Gogebic Taconite wants to mine in the Penokee Hills. The company filed paperwork with the DNR last month outlining a plan to sample rock from five sites to assess the iron deposit's quality.

The DNR sent a letter to the company Tuesday saying the plan will require a storm water discharge permit. The agency said the company may need other permits as well but the plan lacks enough information to know for sure.

The DNR asked for more details, including what kind of explosives would be used, air emission estimates, a wetland inventory for the site and anti-erosion and anti-pollution measures.