June 24, 2013 at 2:03 PM ET
Elevated levels of methane and other stray gases have been found in drinking water near natural gas wells in Pennsylvania's gas-rich Marcellus shale region, according to new research. In the case of methane, concentrations were six times higher in some drinking water found within one kilometer of drilling operations.
"The bottom line is strong evidence for gas leaking into drinking water in some cases," Robert Jackson, an environmental scientist at Duke University in Durham, N.C., told NBC News. "We think the likeliest explanation is leaky wells," he added.