MINNEAPOLIS (AP) — Wisconsin officials have found elevated levels of toxic heavy metals near a frack sand mine spill that sent millions of gallons of sludge into a Trempealeau River tributary.

Department of Natural Resources test results released late Wednesday show high levels of arsenic and other contaminants at the source of a spill at the Hi-Crush mine near Whitehall in western Wisconsin. The mine drained 10 million gallons of water (38 million liters) to rescue a contractor whose bulldozer slid into a pond last month.

Testing near the spill shows arsenic nearly seven times the allowable levels for drinking water. Levels are lower downstream.

DNR spokesman Jim Dick says the department has observed no fish kills and that oxygen levels there can support aquatic life.

Hi-Crush is cleaning up the spill.

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