Activists opposed to the controversial gas drilling process known as "fracking" are hailing an unprecedented direct action that brought a drilling operation in Pennsylvania to a temporary halt. Dozens of activists with the group Earth First! blockaded an access road leading to a well in Pennsylvania’s Moshannon State Forest, stopping operations in an area targeted for heavy drilling. Two activists known as "tree sitters" hung from trees with anchor ropes strung across the access road. Drilling was reportedly suspended for 12 hours at the site before authorities dispersed the protest. Activists say it is the first time protesters have shut down a hydrofracking drill operation in the United States. Hydraulic fracturing, or fracking, involves blasting a mix of sand, water and chemicals into shale rock to extract gas. Opponents say the process imperils drinking water supplies, threatens public health and damages the environment. The protest action comes weeks after activists and residents at the Riverdale Mobile Home Park in Jersey Shore, Pennsylvania, staged a protest encampment against a company that had bought the park and evicted residents to make way for a fracking-related operation.