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EDEN, N.C. — Independent water testing groups are collecting and testing more samples in Dan River after Duke Energy’s “highly toxic” coal ash spill.

Waterkeeper Alliance and Water Defense submerged green foam-like sponges into the Dan River to determine whether or not the river is safe.

Samples dipped in the Dan River Saturday were left to soak for six hours and will be sent to a lab in Cincinnati, Ohio for evaluation.

Chief Chemist Scott Smith with Water Defense said the foam like sponges were used in the BP Gulf of Mexico oil spill and allowed better testing results beneath the surface for extended periods of time.

“This product is bio mimicry of the lungs,” Smith said. “It attracts oil and contaminants like a magnet and compels clear water. It was initially approved by BP in the Gulf of Mexico.”

Duke Energy representative Jeff Brooks said the 50,000 to 82,000 ton coal ash spill Sunday came from a storm water pipe at an inactive part of the plant.

“Last night our crews began installing a permanent plug in the storm drain line and that permanent plug consists of a concrete mixture that has to harden in that area and when it does it will seal the pipe. In fact that is what happened we had confirmation this evening (Saturday),” Brooks said.

Though no specific dates were given, Brooks said Duke Energy is working closely with governmental agencies to continue to monitor the water and prepare for cleanup.

A certified laboratory analysis of water samples taken from the Dan River on Feb. 4 reveal that the water immediately downstream of Duke Energy’s ash spill is “contaminated with extremely high levels of arsenic, chromium, iron, lead and other toxic metals” typically found in coal ash, according to a report from Waterkeeper Alliance.

North Carolina Gov. Pat McCrory visited the Dan River near the site of the spill on Thursday, calling the incident a “serious accident,” but saying that based on Duke water standards and side sampling, the drinking water in the area appears to be safe.

VIEW THE REPORT: Data from ash release at Duke Energy Dan River Station

On Thursday, the Waterkeeper Alliance and Yadkin Riverkeeper issued the results of water sampling from the Dan River in the wake of the third largest coal ash spill in U.S. history.

MORE COVERAGE: Dan River coal ash spill

Authorities said when compared to the levels found in a “background” water sample taken upstream of the spill, arsenic levels immediately downstream of the spill are nearly 30 times higher, chromium levels are more than 27 times higher, and lead levels are more than 13 times higher because of Duke Energy’s coal ash waste.