An EPA study found cancerous compounds, including one used in hydraulic fracturing to harvest natural gas, in an aquifer in Wyoming, ProPublica reports.

The findings come from monitoring wells near Pavillion, Wy., an area where residents have long complained about contaminated drinking water, which some have long blamed on the hundreds of hydraulic fracturing operations in the area.

The area's residents "have alleged for nearly a decade that the drilling -- and hydraulic fracturing in particular -- has caused their water to turn black and smell like gasoline," writes Abrahm Lustgarten, who has covered the fracking debate for ProPublica. "Some residents say they suffer neurological impairment, loss of smell, and nerve pain they associate with exposure to pollutants."

The new findings are not conclusive, but seem to strongly suggest that the fracturing of underground shale to free natural gas has, in some instances, allowed the high-pressure chemical mixtures — and the released gas itself — to leak into the aquifer that supplies the region's fresh water.

The information released yesterday by the EPA was limited to raw sampling data: The agency did not interpret the findings or make any attempt to identify the source of the pollution. From the start of its investigation, the EPA has been careful to consider all possible causes of the contamination and to distance its inquiry from the controversy around hydraulic fracturing.

Still, the chemical compounds the EPA detected are consistent with those produced from drilling processes, including one -- a solvent called 2-Butoxyethanol (2-BE) -- widely used in the process of hydraulic fracturing. The agency said it had not found contaminants such as nitrates and fertilizers that would have signaled that agricultural activities were to blame.

The wells also contained benzene at 50 times the level that is considered safe for people, as well as phenols -- another dangerous human carcinogen -- acetone, toluene, naphthalene and traces of diesel fuel.

The EPA said the water samples were saturated with methane gas that matched the deep layers of natural gas being drilled for energy. The gas did not match the shallower methane that the gas industry says is naturally occurring in water, a signal that the contamination was related to drilling and was less likely to have come from drilling waste spilled above ground.

This could provide rich new material for anti-fracking activists, who have already proved adept at spurring people into opposition. Some water-issues commentators have yet to weigh in, though if Mos Def was serious about the mission to "avoid public panic and freakiness," this might be a good time.