Tokyo Electric Power Co. said Monday a problem with electric power has occurred at its crippled Fukushima No. 1 nuclear power plant, leading to the suspension of the system to cool spent fuel pools of the Nos. 1, 3 and 4 units.

The incident, however, so far has not affected the ongoing water injection to the Nos. 1 to 3 reactors, which suffered core meltdowns in the early days of the March 2011 nuclear crisis, according to the Nuclear Regulation Authority.

No abnormality has been detected in radiation levels in areas surrounding the plant in Fukushima Prefecture.

According to the NRA, Tepco reported to regulators that electricity went out at the plant's accident response center at about 6:57 p.m. Monday.

The power outage at the center was temporary and power to it was soon restored. But Tepco and the NRA were unable to specify immediately why power to the spent fuel pool cooling systems of the three units remains halted.

According to Tepco, the temperatures of the water inside the spent fuel pools of the Nos. 1, 3 and 4 units was between 13.7 C and 25 C at 4 p.m. Monday.

Tepco says that it would take four or five days until the water inside the spent fuel tank at the No. 4 reactor building exceeded 65 C, a temperature level that should not be exceeded.

The No. 4 spent fuel pool, located atop a building damaged by a hydrogen explosion, stores a total of 1,533 fuel assemblies.

The electricity trouble has also led to suspended operation of a facility to clean radioactive water accumulating at the plant, as well as a cooling system at another pool located inside a different building at the site which contains 6,377 fuel assemblies.