"The declaration was made due to an indication of an increase in reactor coolant system leakage," the NRC said in a statement. No radiation was released and the plant is maintaining the appropriate water level in the reactor, the NRC said.
The "unusual event, declared at 6:24 a.m., is the lowest emergency level declaration made by the agency.
Two NRC inspectors were monitoring reactor, which is currently shut down for refueling. Unit 1 at the power plant is operating at full power, The (Redwing) Republican Eagle said.
The two-unit nuclear power station -- in Welch, 26 miles southeast of Minneapolis -- is owned and operated by Northern States' Power Co., a unit of Xcel Energy.