The Nuclear Regulation Authority has ordered its secretariat to thoroughly investigate the cause of damage to a nuclear power plant from the 7.6 magnitude earthquake that struck the Noto Peninsula on Jan. 1.

The regulatory watchdog gave the order at a regular meeting on Wednesday.

According to Hokuriku Electric Power, the quake measured an upper 5 on the Japanese seismic intensity scale at the basement of the No. 1 reactor building of its Shika nuclear power plant in Ishikawa Prefecture.