Security equipment failed temporarily at the Prairie Island nuclear power plant, triggering an "unusual event" report to federal regulators, plant owner Xcel Energy said Wednesday.

In a statement, the Minneapolis-based company said no radioactive material was released from the plant near Red Wing, Minn., and there was no danger to the public or plant employees.

Plant security was maintained and plant officials were evaluating the cause of the failure, Xcel said. The equipment that failed was not specified.

An unusual event declaration is the lowest of four emergency classifications established by the U.S. Nuclear Regulatory Commission, indicating a potential safety reduction, but no public safety threat.