ST. PAUL, Minn. (AP) — Minnesota health officials said Thursday that they had improperly tested thousands of water samples for decades and would re-evaluate hundreds of sites across the state for fertilizer, cyanide and other chemicals.

The error revolves around water temperature. Federal guidelines issued in the 1990s say testing for some organic chemicals, such as fertilizer and common household chemicals, along with other chemicals like cyanide and nitrite should be carried out on water at about 40 degrees. Health Commissioner Ed Ehlinger said officials discovered this week that Department of Health staff members have not always followed procedure, testing samples at higher temperatures that can show lower levels of contamination.

It’s unclear how many tests were performed incorrectly, though Ehlinger put the likely sum in the thousands. The inconsistency doesn’t involve lead testing, but the water crisis in Flint, Michigan, has state officials across the nation on high alert about water quality.

“We don’t believe there’s a significant health risk, but we need to make sure there’s an accurate health picture of our water quality,” Ehlinger said. “We should have picked this up earlier.”

State officials said they’ve already instituted more rigorous standards for future evaluations and would comb through prior tests to find how many samples were improperly tested. They’ve already started shuffling staff to handle a new round of tests at the community water systems deemed most vulnerable.

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