North Carolina Gov. Bev. Perdue (D) on Sunday announced that she had vetoed a controversial bill that would have legalized fracking in the state.

Senate Bill 820, which was championed by Republican lawmakers, would have legalized the method of releasing natural gas by injecting water, sand and chemicals into the ground. The law would have given regulators two years to come up with safeguards, but critics argued that the rules should be in place before the practice was legalized.

"This bill does not do enough to ensure that adequate protections for our drinking water, landowners, county and municipal governments, and the health and safety of our families will be in place before fracking begins," Perdue said in a statement.

"I urged the sponsors of the bill to adopt a few changes to ensure that strong protections would be in place before any fracking would occur," she continued. "The General Assembly was unwilling to adopt the changes I suggested. Therefore, I must veto the bill."

By Sunday evening, the conservative group Americans for Prosperity had already released a robocall asking North Carolinians to urge their state representatives to override Perdue's veto.

In addition to posing a threat to drinking water, hydraulic fracturing can cause earthquakes, according to a National Research Council report released last month.

Listen to this audio from Americans for Prosperity via WRAL, broadcast July 1, 2012.