CANONSBURG, Pa. - People who make a living from a natural gas drilling technique that involves pumping chemical-laced water into the earth and others who believe it has poisoned them or their well water packed into a hotel ballroom in southwestern Pennsylvania on Thursday night to make an impression on federal researchers.

Residents of Hickory, about 15 miles southwest of Pittsburgh, called for intensive study of hydraulic fracturing, or fracking, and told a U.S. Environmental Protection Agency panel that their well water turned foul after drilling began nearby in the last few years.

In fracking, drilling crews pump millions of gallons of sand- and chemical-laced water deep into the earth to break up dense rock to free the natural gas. Some of that water returns as a briny, chemical- and metal-laden brew and is usually stored in open pits until it's trucked to treatment plants or underground injection wells.

The oil and gas industry steadfastly defends the fracking process as having been proven safe over many years and says it is a crucial tool if the country is going to be able to harvest its gas reserves.