All nuclear power plants in Japan were unaffected as of 9:20 a.m. by the strong earthquake that rocked Osaka and neighboring prefectures on the morning of June 18, the Nuclear Regulation Authority said.

The temblor, which struck at 7:58 a.m., recorded a lower 6 on the Japanese seismic intensity scale of 7 in northern Osaka Prefecture.

Kansai Electric Power Co. restarted the Oi nuclear plant in Oi and the Takahama nuclear plant in Takahama in Fukui Prefecture, north of Osaka Prefecture, in recent months.

The area where the two plants are located recorded seismic intensities of 3 to 4, which were not strong enough to trigger an automatic shutdown.

Kansai Electric has been operating the No. 3 reactor at the Takahama plant and the No. 3 and No. 4 reactors at the Oi plant. The No. 4 reactor at the Takahama plant has been offline for a regular inspection since May.

No abnormalities have been reported from radiation monitoring posts installed around the nuclear plants.