MINNEAPOLIS (AP) — Xcel Energy Inc. has shut down two of Minnesota's three nuclear reactors.

The Monticello plant had been operating at 10-percent power since the weekend, and operators shut down Prairie Island's Unit 1 plant Tuesday.

Xcel says both shutdowns were done safely. The Minneapolis-based utility says neither resulted in a release of radioactive materials and did not pose a danger to the public or plant employees.

At Prairie Island, a test found emergency diesel generators were inoperable.

Workers closed the Monticello plant after discovering leakage which apparently was caused by a failing gasket on a pipe flange.

Xcel says the leaked material was contained within the containment structure.

The company is buying power on the open market, and says repairs will not take long.

Copyright 2012 The Associated Press.