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Despite previous claims, contaminated groundwater found in areas of Pennsylvania and Texas was not caused by controversial fracking drills.

Instead, the tainted water supplies are being blamed on problems in pipes and seals in nearby natural gas wells. 

Experts focused on eight hydraulically fractured wells in both states, and used chemical analysis to determine when in the process of gas extraction methane leaked into groundwater.

Researchers claim the drilling procedure called fracking didn't cause water in Texas and Pennsylvania to become contaminated. Instead, they blamed the methane levels on leaky wells. Fracking operations at a wellpad overlying the Marcellus Formation in Pennsylvania pictured

'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 added those results are good news because this type of contamination problem is easier to fix and is more preventable than the damage caused by fracking. 

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

Earlier this year, residents began accusing the fracking process for the contamination, claiming the fracturing allowed methane to travel up, outside the pipes, into water supplies.

In at least two cases around a well in Texas, scientists saw methane levels in people's home jump ten-fold during the year of study.  

'I don't think homeowners care what step in the process the water contamination comes,' Stanford University environmental sciences professor Rob Jackson said.

'They just care that their lives have changed because drilling has moved next door.'

Since the fracking began in Pennsylvania in 2008, the state has identified 243 cases of private water supply contamination 'impacted by oil and gas activities' - out of more than 20,000 wells drilled in the region.

Jackson and colleagues have been studying water contamination around natural gas wells for years, but rather than choosing random samples for this particular study, his team aimed their research at areas with the most contamination complaints.

And even in those areas, it was only in a minority of dozens of sites that they could they connect the contamination to the natural gas wells, he said. 

Experts reached their conclusions by chemically analysing methane and other chemicals in the groundwater in Texas (pictured) and Pennsylvania. They could then link the contamination to particular wells, and then to discover what part of the drilling process was responsible

This graphic reveals how gas is extracted from the ground using fracking techniques

In some cases, the contamination was natural and had no connection to gas wells, Jackson said.

Terry Engelder, a professor of geosciences at Pennsylvania State University who wasn't part of the study, praised it, saying 'focusing on frack fluids at depth is not the real problem.' 

It is possible the high pressure of fracking or the bends in unconventional wells could lead to problems with the well's piping, but there's no evidence yet proving that, Jackson added. 

Another issue could be the hurry drillers are in during a boom, leading to poor quality wells, he said. 

Dave Spigelmyer, president of the Marcellus Shale Coalition of drillers, said his industry is working with state officials 'to modernize and dramatically strengthen shale development-related regulations.'

Cornell University engineering professor Anthony Ingraffea, who wasn't part of the study, praised it, adding that he's worried because 'it's impossible to drill and cement a well that will never leak.'

'There's still serious and signiicant harm from what's coming before fracking and what's coming after fracking,' Ingraffea said.

The findings were published in the The Proceedings of the National Academy of Sciences journal.