A new Department of Energy study may provide some of the first solid answers to an extremely controversial question: Do gas drilling fluids migrate and pose a threat to drinking water?

Department spokesman Richard Hammack says a gas drilling company in southwestern Pennsylvania has let researchers add tracing compounds to the fluids used in hydraulic fracturing, or fracking.

The well is tapping the gas-rich Marcellus Shale. Hammack says researchers will be able to see if the drilling fluids move upward or sideways from the well bottom, which is 8,100 feet deep.

Environmentalists say the fluids associated with drilling can rise and pollute shallow drinking water aquifers.

The industry and many state and federal officials say the practice is safe when done properly, but there have also been cases where faulty wells did cause pollution.