A new federal study concluded there’s no evidence that suggests oil and gas production in northern Pennsylvania has contaminated the state forest service’s rivers and streams, according to Kallanish Energy.

The study was published earlier this month in the scientific journal Proceedings of the National Academy of Sciences (PNAS). It found no signs wastewater from fracked wells had entered any of more than two dozen streams running through the Marcellus.

The study’s authors included representatives from the Bureau of Forestry within the Pennsylvania Department of Conservation and Natural Resources, and the Division of Water Quality at the Pennsylvania Department of Environmental Protection.

Learn more: Kallanish Energy > Study finds no evidence fracking waste harms streams