KEYSTONE, S.D. (AP) - Work has resumed at a gold exploration drilling site in western South Dakota where a leak occurred last week.

The site was shut down when bentonite leaked into Battle Creek near Keystone. Bentonite is a claylike material used as a drilling lubricant. The Rapid City Journal reports (http://bit.ly/11ML8oH) that state officials do not expect any environmental damage.

Mineral Mountain Resources Ltd. of Vancouver, British Columbia, is exploring for gold in the area.