Xcel Energy says its Monticello nuclear power plant automatically shut down Tuesday, Sept. 25, for unknown reasons. The shutdown occurred at 11:07 a.m. and all plant safety systems were functioning, the Minneapolis-based utility said Tuesday. The shutdown posed no danger to the public or the plant’s workers, Xcel officials said. The cause of the shutdown is under investigation. Xcel said it has notified the Nuclear Regulatory Commission and the state. Monticello is located about 40 miles northwest of Minneapolis. The 600-megawatt boiling water reactor plant was last shut down in August for seven days due to a leaking gasket on a pipe flange. Monticello also had a three-week shutdown last year that started on Nov. 19 when safety systems detected low oil pressure in the plant’s turbines, Xcel said at the time of the incident. In both previous shutdowns, Xcel said there was no danger to the public or workers. Monticello generates enough electricity to supply almost 500,000 homes. Xcel officials said the current shutdown is not expected to be lengthy.