RALEIGH, N.C. (AP) — The nation’s largest electricity provider and an environmental group are reporting conflicting data about the levels of toxins detected in a North Carolina river following a massive spill of coal ash.

Duke Energy said Thursday its results from the Dan River downstream from the company’s power plant in Eden showed traces of arsenic contamination, but at levels considered safe for both people and aquatic life.

The closest samples the company collected were about two miles downstream from where about 82,000 tons of toxic coal ash has spilled into the river. The spill was discovered Sunday and is ongoing.

Water samples tested by a certified lab hired by the Waterkeeper Alliance contained hazardous levels of arsenic 10 times higher than Duke’s readings. Those samples were collected yards from the spill site.