ST. PAUL, Minn. (AP) — Minnesota health officials are reviewing their water quality testing after discovering they evaluated samples at temperatures too hot to detect some chemical contaminants.

Testing for chemicals like fertilizer, cyanide and nitrite is supposed to be performed on water at roughly 40 degrees. But the Minnesota Department of Health said Thursday it has transported some samples at room temperature, at which some tests may show lower levels of contamination.

Health commissioner Ed Ehlinger says the error is unlikely to mean more risk for residents.

It's unclear how many tests were performed incorrectly since the federal government's temperature guidelines in the 1990s. It doesn't involve lead testing, but the water crisis in Flint, Michigan has prompted extra scrutiny.

The state is reviewing how many samples were improperly tested and re-doing some evaluations.

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