WASHINGTON — The drilling procedure called fracking didn’t cause much-publicized cases of tainted groundwater in areas of Pennsylvania and Texas, a new study finds. Instead, it blames the contamination on problems in pipes and seals in natural gas wells.

After looking at dozens of cases of suspected contamination, the scientists focused on eight hydraulically fractured wells in those states, where they chemically linked the tainted water to the gas wells. They then used chemical analysis to figure out when in the process of gas extraction methane leaked into groundwater.

“We found the evidence suggested that fracking was not to blame, that it was actually a well integrity issue,” said Ohio State University geochemist Thomas Darrah, lead author of the study. He said those results are good news because that type of contamination problem is easier to fix and is more preventable.

The work was released Monday by The Proceedings of the National Academy of Sciences.

In fracking, highly pressurized chemicals and water are pumped deep underground to break shale and release natural gas for harvesting.

The fracking process has become highly charged. It started a boom of natural gas drilling and with it, an initial surge of reports of water contamination nearby. People blamed the fracking process, thinking that the fracturing allowed methane to travel up, outside the pipes, into water supplies.

In at least two cases around one well in Texas, scientists saw people’s homes have their water supplies go from clean to contaminated during the year of study, with methane levels jumping ten-fold, said Stanford University environmental sciences professor Rob Jackson, co-author of the study. Methane, while not particularly toxic, is explosive and a potent greenhouse gas.

“I don’t think homeowners care what step in the process the water contamination comes,” Jackson said. “They just care that their lives have changed because drilling has moved next door.”

The scientists reached their conclusions by chemically analyzing methane and other chemicals in the groundwater. That let them link the contamination to particular wells, and then to discover what part of the drilling process was responsible. For example, they studied the precise proportions of methane, helium, neon and argon. Those proportions pointed to leaky pipes and seals, because the results would have been different if the contamination had come from fracking.

Since the fracking boom started in Pennsylvania in 2008, the state has identified 243 cases of private water supply contamination “impacted by oil and gas activities.” That is out of more than 20,000 wells drilled there.

Jackson and his colleagues aimed at areas that seemed to have most complaints of contamination.

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