TOKYO - Tokyo Electric Power Company Holdings Inc. said early Friday that it has shut down a reactor at the Kashiwazaki-Kariwa nuclear power plant after an alarm was triggered during control rod withdrawal operations around five hours and 25 minutes after it was restarted.

The reactor is the first to be restarted by TEPCO since the 2011 Fukushima nuclear disaster. The resumption came on Wednesday, a day later than initially planned, after a control rod alarm sounded during a final pre-startup test.