SIOUX FALLS, S.D. (AP) — South Dakota officials acted prematurely in reporting that human health wasn't at risk from high ammonia releases at a Sioux Falls plant, according to water quality advocates.

Ammonia was released into the Big Sioux River following a wastewater treatment system failure at the Smithfield Foods pork processing plant last week. The South Dakota Department of Environment and Natural Resources issued a statement Friday that there was no risk to humans, though fish could be threatened.

Ammonia is used in industrial processes and can treat water. But high doses in water can cause neurological and liver problems, according to the National Institutes of Health.

Advocates have said the statement was released before the ammonia violations stopped and before the source of the problem was identified, The Argus Leader reported . The statement was also made before ammonia release peaked, advocates said. The plant is permitted to release 102 pounds of ammonia per day, but it released 2,199 pounds Saturday.

"That's an inadequate response from the DENR, because they didn't have the data to make that statement one way or the other and should have erred on the side of human health," said Dana Loseke, a leader of the Friends of the Big Sioux River advocacy group. "The amount of ammonia that was released, and that they were allowed to continue to release that amount, was obscene."

Kelli Buscher, an administrator for the state's Surface Water Quality Program, said the state took immediate and appropriate action after Smithfield officials reported the ammonia discharges. The state worked with the plant to reduce discharges and sent inspectors to sample water several times at four different locations near the plant, she said.

Smithfield officials also said there was no risk to human health or wildlife.

"Smithfield takes environmental compliance very seriously and strives for 100 percent compliance, 100 percent of the time," the company said.

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Information from: Argus Leader, http://www.argusleader.com