PITTSBURGH — The U.S. Geological Survey said Tuesday that the Marcellus Shale region contains some 84 trillion cubic feet of undiscovered, recoverable natural gas, far more than thought nearly a decade ago.

Tuesday’s figure is much higher than the last government assessment in 2002, which suggested about 2 trillion cubic feet of recoverable gas.

The USGS said the estimate came from new information about the gas-rich formation underlying New York, Pennsylvania, Ohio and West Virginia, and from technical improvements in how wells are drilled.

Environmental groups have expressed concerns that the process of extracting the gas from deep underground could contaminate the water supply. But gas industry groups welcomed the independent government estimate.

“While some critics continue to question the viability of responsible domestic shale gas development, it is abundantly clear — as laid out by this new data — that the Marcellus Shale will continue to lead the way in meeting American’s energy needs for years to come,” said Kathryn Z. Klaber, president and executive director of the Marcellus Shale Coalition, an organization of energy companies that says it’s committed to the responsible development of natural gas from the shale formation and the enhancement of the region’s economy.

The agency also estimated there are around 3.4 billion barrels of undiscovered, recoverable natural gas liquids. That product attracts a premium price over the natural gas.

More than 3,300 wells have been drilled across Pennsylvania in just the last few years.