A government panel on Thursday August 11, 2011  called the risk of water pollution from natural gas fracking "remote."

The U.S. Energy Department's natural gas advisory subcommittee urged regulators to require drillers to detail what chemicals they use in hydraulic fracturing -- which involves blasting a mix of water, sand and chemicals into rock formations to release oil and gas -- and release more information about the drilling technique's impact.

Environmental activists and communities where the technique is used have made a host of claims about the harm fracking has done or could do in their areas, ranging from drinking water contamination to causing unusual earthquakes.

Here are some of the environmental concerns stemming from natural gas fracking:

DRINKING WATER

A key concern for environmental and community groups is the possibility that chemically treated water used in fracking could wind up in sources of public drinking water.

In New York and Pennsylvania, which house much of the Marcellus Shale gas reservoir, researchers from Duke University in May reported finding potentially harmful concentrations of methane near drilling sites.

The Energy Department panel downplayed those concerns in its interim report on Thursday, writing that it "shares the prevailing view that the risk of fracturing fluid leakage into drinking water sources...is remote."