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A law signed this week in Texas now prohibits cities and towns from banning fracking and other activities that harvest oil and natural gas.

The law was drafted after voters in Denton, a city outside Dallas, banned "hydraulic fracturing" locally in 2014.

Fracking opponents warn that potential carcinogens used in the extraction process may contaminate groundwater.

Similar bills are being considered in US states including Colorado, Ohio, Oklahoma and New Mexico.

Republican Texas Governor Greg Abbott called the anti-fracking measures heavy handed regulations.

"This law ensures that Texas avoids a patchwork quilt of regulations that differ from region to region, differ from county to county or city to city," Mr Abbott said.

Fracking is the process of drilling down into the earth before a high-pressure water mixture is directed at the rock to release the gas inside.

Water, sand and chemicals are injected into the rock at high pressure which allows the gas to flow out to the head of the well.

In addition to concerns about groundwater, studies have found that fracking can cause small earthquakes.

Image copyright AFP Image caption Opponents say fracking is harmful to the environment

Supporters of fracking say the extraction occurs thousands of feet beneath drinking water, where chemicals pose no risk.

Two of the most productive US shale oil fields are located in north Texas near Denton. The law was backed by oil and gas interests.

"The state of Texas has failed to stop Big Oil from polluting our air and water, causing earthquakes, and putting our families at risk from leaks, spills and explosions," Environment Texas Director Luke Metzger told the Dallas Morning News.

Calls for more regulations on fracking in the US are growing.

In 2013, the Pennsylvania state Supreme Court overturned a measure similar to the new Texas law, and the state's governor Tom Wolfe has promised more oversight over the industry.

New York state banned fracking in December. Maryland lawmakers passed a veto-proof 2 1/2 year moratorium in April. The governor has yet to make a decision on the bill.