A nuclear power plant in Washington state was restarted on Thursday after being shut down earlier this week after a maintenance test found an issue with a valve.

The Columbia Generating Station in Richland, owned by Energy Northwest, is currently operating at around 24 percent power, public affairs supervisor John Dobken told Reuters.

The plant, Washington's third-largest electricity generator, is expected to be running at 100 percent power by the weekend, Dobken added.

The plant was taken offline on Monday after a maintenance test revealed a valve connected to a secondary cooling system that cools pumps and heat exchangers was not isolated properly before testing and triggered an alarm.

The power plant provides power to 27 public utility districts and municipalities.

Dobken said the shutdown had not posed any safety issues.

The last time the Columbia Generating Station saw an unplanned shutdown was in November 2009, for a couple of days.