Environmental Protection Agency science advisers want the agency to provide quantitative proof that fracking doesn't pollute the water table after the agency already said there is no evidence it does.

The EPA Scientific Advisory Board, a key federal panel of advisers, said late Thursday that the draft fracking report the agency released a year ago needs to back up its claims with statistical data and quantitative analysis that fracking has had no "widespread" impact on the water table.

The EPA draft report, which has not been finalized, concluded that there was no evidence to support that hydraulic fracturing, otherwise known as "fracking," has led to widespread, systemic effects on the nation's drinking water.

The draft report conceded that there were some isolated issues, but all of those were "small compared to the number of hydraulically fractured wells."

Fracking is a method of oil and gas drilling that uses a combination of sand and water injected deep underground to break up shale rock formations. The oil and natural gas are released once the stone is broken up and fractured. The process has made the U.S. a global leader in oil and gas production.

The EPA's conclusion has widely been taken to mean that fracking poses no threat to the nation's water supply.

But the 30-member Scientific Advisory Board appears to be questioning whether that assessment should be the final say on the matter.

In its comments on the EPA's draft report Thursday, the panel said the report was "comprehensive but lacking in several critical areas." It recommended the EPA go back and provide a rigorous "quantitative analysis that supports its conclusion," essentially forcing the agency to defend its conclusion.

Twenty-six members of the board voted to press the agency, while only four members dissented.

The oil and gas industry pushed back against the advisers Friday, saying the EPA's analysis is solid and does not require further analysis.

"The science is clear and the studies are completed," said Erik Milito, the head of upstream and industry operations for the American Petroleum Institute. "Study after study shows that hydraulic fracturing is safe."

The group added that the draft report affirms the scientific data through a rigorous process from nearly 1,000 sources of information, published papers and technical analysis, and even other peer-reviewed EPA scientific reports, to show "no widespread, systemic impact on the quality of drinking water."

Milito underscored that in addition to posing no threat to the drinking water, fracking is helping to reduce emissions blamed for causing global warming and climate change. Many scientists blame the burning of fossil fuels for warming the Earth, resulting in more severe weather, floods and drought.

"The benefits of hydraulic fracturing have made the United States the No. 1 producer of oil and natural gas in the world, and largely due to affordable and abundant supplies of natural gas, we are also leading the world in reducing carbon and other emissions," Milito said.

"Instead of denying the scientific evidence proving the environmental benefits of hydraulic fracturing, the United States should be celebrating the overwhelming data demonstrating that hydraulic fracturing is helping reduce [greenhouse gas] emissions and other emissions, and has helped lower energy costs for consumers," he said.

Meanwhile, environmental groups and fracking opponents welcomed the science advisers' recommendation. Many climate activists and anti-fossil fuel groups have opposed the EPA's findings, which they say were influenced by the energy industry's over-involvement in the process.

"We are calling on the EPA to act quickly on the recommendations from the EPA [science board] and be clear about fracking's impacts on drinking water resources," said Hugh MacMillan, senior researcher at Food and Water Watch.

MacMillan's group is part of the coalition called Americans Against Fracking, which wants the EPA to either quantify that fracking has had no "widespread" effects, as the panel recommends, or drop its finding altogether.

"The EPA must prioritize the health and safety of the American people over the political interests of the oil and gas industry and its financiers, who have committed hundreds of billions to drilling and fracking in the coming decades," MacMillan said. "For climate reasons alone, that's a vision for the future that we can ill-afford."

The group argues that fracking is increasing the amount of fossil fuels being burned and is raising the amount of greenhouse gas emissions that many scientists blame for climate change.