CHARLOTTE, N.C. – Duke Energy confirmed Wednesday that tests have shown trace amounts of radioactivity in groundwater around some of its coal ash plants.

The results were posted in documents filed with the federal Environmental Protection Agency.

The EPA mandated Duke and other coal-fired plant operators to drill test wells to monitor and test for groundwater pollution.

Duke spokesperson Erin Culbert said there are no causes for residents to be alarmed by the findings.

“Its really important to note that neighbors around our facilities remain perfectly safe,” she told NBC Charlotte.

The Catawba Riverkeeper, an environmental organization, said in a statement that Duke’s test results found, “levels of radiation from radium at the Marshall coal-fired plant on Lake Norman were 2.5 times the federal drinking water standard.”

Culbert said that was true.

“The data is true," she said. "We do have that level in the groundwater near the basin. What we have yet to decide is whether that is naturally occurring or whether that’s actually from the coal ash itself.”

But Catawba Riverkeeper Sam Perkins said the answer is obvious.

“Duke can say that its uncertain but the fact is that 11 of 18 sites have this problem. Additionally, we don’t see the problem in groundwater, even around their nuclear sites,” he said.

Hundreds of families living around Duke coal ash plants are using bottled water that Duke provides.

Said Perkins, “We really need to get this stuff out of the ground and away from the banks of our drinking water.”

But Culbert said the Riverkeeper is going too far.

“To really alarm the community and let folks believe that their drinking water is unsafe is irresponsible,” she said.