Fracking is a way for the natural gas industry to drill deep into shale gas deposits, but some worry that the gas itself and the fluids used in the process may contaminate local drinking water supplies. Reuters/Jason Cohn

Voters in three out of four cities in Colorado where a fracking ban was on the ballots on Tuesday chose to say no to the controversial technique of extracting oil and gas from the ground by injecting a mix of water, air and chemicals.

More than 76 percent of voters in Boulder voted in favor of extending a five-year ban on hydraulic-fracturing, or fracking as it is popularly known, inside city limits, and more than 55 percent of Fort Collins voters supported a five-year ban on fracking, while about 58 percent of Lafayette residents voted in favor of an amendment that will ban fracking permanently within their city limits. However, in Broomfield, the anti-fracking measure failed narrowly -- by 194 votes -- with 50.51 percent of voters saying no to a moratorium on fracking.

"The voters are saying that they don't buy the idea that corporate interests are superior to public health, property values, quality of life and democratic self-determination," Cliff Willmeng, an anti-fracking activist, told Daily Camera.

A New York Times report, citing unofficial results obtained from county clerks, said on Wednesday that a similar ballot to ban or restrict fracking had failed in two out of three cities in the state of Ohio.

Anti-fracking activists claim that fracking inside city limits causes pollution and contaminates groundwater, and poses health risks, while the industry's supporters argue that there is no evidence of health risks associated with fracking.

“When you have an industry that is exempt from the most basic provisions of the Safe Drinking Water Act and the Clean Air Act, something is obviously wrong. This says that the fracking industry cannot survive unless it passes the cost of doing business--be it health effects or air and water contamination--onto the communities in which they are drilling in,” Russell Mendell, Statewide Director of Frack Free Colorado, said in a statement.

According to various reports, millions were spent in the last two months by the fracking industry and anti-fracking factions in Colorado on their campaigns ahead of the elections, and in most cities, the pro-fracking Colorado Gas and Oil Association, outspent anti-fracking activists.

“Well today Colorado residents have shown that they can decide for themselves whether or not they want fracking in their communities. COGA's millions will not change that," Mendell said.

However, observers point out that public sentiment in other Colorado cities, especially in Republican-dominated regions, against fracking could be different.

"As the debate moves from places like Boulder and Lafayette -- which come with highly Democratic constituencies -- to purple Colorado, you're going to see a different outcome," B.J. Nikkel, a former State House representative, told Daily Camera. "This is round one in a much longer match."