The operators of the Wolf Creek nuclear power plant say a loss of off-site power prompted an automatic shutdown at the northeast Kansas facility.

The shutdown happened Friday afternoon. Wolf Creek officials say the plant’s two emergency diesel generators automatically started, supplying power to all safety-related equipment.

Plant officials declared a “notification of unusual event,” which is the lowest of 4 emergency classifications defined by the Nuclear Regulatory Commission.

Wolf Creek is owned by Kansas City Power & Light Co., Topeka-based Westar Energy and the Kansas Electric Power Cooperative. During a shutdown, the companies rely on other generating plants they own or buy electricity from other utilities.