The study finds that eight hydraulically fractured wells in the states of Pennsylvania and Texas leaked gas because the piping and cement seals in the wells themselves weren't working properly.
The process of pumping highly pressurized chemicals and water underground to get valuable natural gas trapped in shale has become highly charged as contamination complaints initially surged.
Ohio State University geochemist Thomas Darrah and colleagues used certain elements to trace where the leaks came from. He said finding them in the wells rather than the fracking process, means contamination is more preventable and fixable.
The study is published in Monday's Proceedings of the National Academies of Sciences.