On September 2, the EPA released data showing that water and sediment samples taken from the San Juan River — whose largest tributary, the Animas River, was tainted with three million gallons of toxic wastewater from the Gold King Mine spill earlier this summer — had returned to pre-spill levels. On September 16, during a hearing before the U.S. Senate Committee on Indian Affairs, EPA administrator Gina McCarthy reiterated those findings.

But a spate of recently released studies paint a less positive picture of the river’s return to health. According to Al Jazeera, a new report conducted by the nonprofit Water Defense shows elevated levels of nearly a dozen metals and chemicals still present in the San Juan River. Another study recently conducted along a 60-mile stretch of the Animas River itself by researches at Texas Tech University and New Mexico State University also found elevated levels of heavy metals in the river sediment.

“I would say at this point the water is unsafe to use until we have more testing completed,” Scott Smith, the chief scientist with Water Defense, told Al Jazeera. “We are dealing with known chemicals that are toxic and cancer causing, and we don’t know what’s happening to those chemicals and what’s going on in the crops.”

Water Defense’s tests showed levels of chromium at 4.7 parts per million in sediments affected by the spill, compared to levels of 3.7 parts per million in baseline sediments. According to EPA standards, levels at or below 0.01 parts per million are considered safe for drinking. The Water Defense tests also found concentrations of lead in the San Juan River had increased from 7.8 parts per million to 9.9 parts per million.

The tests also confirmed that the San Juan riverbed was likely contaminated before the spill, Smith told Al Jazeera.

“The sediment showed levels of contamination before, but now it’s a hell of a lot worse after this spill,” Smith said.

The EPA did not respond to ThinkProgress’ request for comment, though an agency spokesperson told Al Jazeera that the agency stands by its testing results. The agency has been harshly criticized for the spill — EPA workers accidentally caused the spill, and the agency initially grossly underestimated the amount of toxic water released by the spill.

The EPA has taken responsibility for its errors, with McCarthy telling the U.S. Senate Committee on Indian Affairs that “the EPA has and will continue to take responsibility to help ensure that the Gold King Mine release is cleaned up.”

While the EPA has shouldered responsibility for the spill, the event highlights larger issues with the an outdated law that dictates the regulation of old mines. Under the General Mining Law of 1872, companies are free to extract minerals from U.S. public lands without paying royalties, and are often not responsible for cleaning up those mines. That has left around 2,700 hard rock mines in the United States in need of cleanup.