CASPER, Wyo. (AP) — A utility says groundwater beneath three coal-fired power plants in Wyoming has tested positive for certain contaminants.

The substances include arsenic and cadmium near the Dave Johnston power plant near Glenrock, lead and selenium at the Jim Bridger plant northeast of Rock Springs, and radium at the Naughton plant outside Kemmerer.

The toxins occurred beneath unlined coal-ash disposal ponds. Coal ash is a byproduct of burning coal in power plants.

Rocky Mountain Power reported the toxins to state regulators this month.

Rocky Mountain Power spokesman Spencer Hall tells the Casper Star-Tribune the coal ash disposal ponds have not to date contaminated drinking water or surface water.

Hall says the company will present a plan to address the contaminants next year.