Brazil's National Petroleum Agency, or ANP, published regulations Wednesday governing the use of the natural gas drilling technique known as hydraulic fracturing, or "fracking."

The regulations state that the extraction of non-conventional, or shale, gas via that method must not harm the environment or human health, the ANP said in a statement.

Among other restrictions, fracking is prohibited at a distance of less than 200 meters (655 feet) from water wells that are used for irrigation, for domestic, public or industrial consumption, or as drinking troughs for animals.

Fracking wells also must be cased with cement to prevent the leaking of gases associated with that drilling technique, which has come under fire from environmentalists in the United States.

Fracking involves pumping a pressurized fluid - usually composed of water, sand and chemicals - into a shale formation to create a fracture in the rock layer and release trapped petroleum or natural gas.

Environmentalists contend that fracking pollutes aquifers and causes earthquakes in the areas where drilling takes place.

Prior to drafting the regulations, the ANP held a 30-day public consultation process in which it gathered 150 comments and suggestions from companies, ordinary citizens and civil society organizations.

The ANP last November awarded an initial batch of non-conventional natural gas exploration blocks in an auction aimed at spurring studies to identify basins containing these hydrocarbon reserves. EFE