TOKYO (Kyodo) -- Tokyo Electric Power Company Holdings Inc. said Monday it will postpone until an unspecified date the restart of its nuclear reactor northwest of Tokyo -- its first since the 2011 Fukushima disaster -- due to a control-rod alarm failure.

The Kashiwazaki-Kariwa nuclear complex in Niigata Prefecture was initially set to restart on Tuesday, but an alarm designed to sound when two or more control rods are withdrawn from the reactor fuel core failed to trigger during a test Saturday, the utility said at a press conference.

The company said it will announce a new date for restarting the No. 6 unit of the nuclear power complex.

After the latest incident, which was deemed a deviation from operational limits stipulated in the plant's safety regulations, TEPCO returned all control rods to the fully inserted position.

The cause of the error was determined to be an incorrect alarm setting that has since been corrected, and the plant was returned to its pre-deviation state Sunday night, TEPCO said.

The rescheduling came as it will take several days for the operator to conduct verification checks on each of the 205 control rods at the No. 6 reactor and examine the fission reaction of the fuel assemblies.

The reactors at the seven-unit complex have been offline since the No. 6 unit entered regular inspection in March 2012.