A pump to inject water into one of the severely damaged reactors at the Fukushima No.1 nuclear complex halted Monday after a worker accidentally triggered a power failure, Tokyo Electric Power Co. said.

The halt occurred at around 9:47 a.m. but cooling of the No. 1 reactor immediately resumed through a backup pump, Tepco said.

The utility said the power failure occurred when one of two employees conducting routine checks of electricity equipment wrongly pushed a "stop" button on a switchboard, cutting power supply.