The Monticello nuclear power plant was automatically shut down over the weekend as a result of safety concerns, Xcel Energy officials said Sunday.
The plant, owned and operated by Xcel, shut down at 11:12 p.m. Saturday when relays that are part of the reactor protection system activated, the company said, adding that all plant safety systems functioned as designed, and the situation posed no danger to the public or to plant workers.
Plant operators are investigating what caused the relays to activate. The shutdown was not expected to be lengthy.
The plant is about 40 miles northwest of Minneapolis. It generates enough electricity to power nearly 500,000 homes.
Xcel will purchase energy from other sources until the plant comes back online.