RED WING, Minn. — Officials say a 2-inch break in a pipe leading to a chlorine bleach tank is to blame for a chemical spill at the Prairie Island nuclear plant near Red Wing.

They say a plant worker discovered the break, leading to an alert being declared shortly before 4 a.m. Thursday. They say public safety was never at risk and no radiological material was released.

About 500 gallons of the chemical, which is used to clean river water needed to cool the plant, spilled. The chemical can cause respiratory problems, but plant officials say no workers were hurt.

An alert is step two in a four-tier system of classifying plant incidents. Xcel Energy’s chief nuclear officer, Dennis Koehl, says it’s the first time an alert has been issued for Prairie Island.