Xcel Energy Inc. said Tuesday that units at its two nuclear power plants in Minnesota have resumed operation after being shut down last week.

The Minneapolis-based utility said Prairie Island Unit 1 near Red Wing, Minn., went back on line and is ramping up to full power. Workers there first repaired exhaust leaks discovered in two diesel backup generators.

Xcel said the single-unit Monticello nuclear power plant returned to full power at 10:45 a.m. Monday, after workers repaired a leaking gasket on a pipe flange.

Although the Prairie Island plant shutdown caused a release of steam last Tuesday that alarmed some residents, the company said all plant safety systems functioned as designed and the public was not at risk.

Prairie Island Unit 2 was not affected and has been running at full power, Xcel said.