Water has leaked out of spent fuel pools at the Onagawa nuclear plant after a second earthquake hit the north-east of Japan.
According to plant operator Tohoku Electric Power, water leaked from spent fuel pools in the plant's No.1, No.2 and No.3 reactors that had been shut down following the magnitude 9.0 quake last month.
Water has also leaked in three other locations in the No.3 reactor complex, according to Reuters.
A small rise in radiation levels inside the reactor buildings has been detected, while there has been no change in radiation levels outside the reactor buildings.
Two out of three lines supplying off-site power to the Onagawa site have been lost in Thursday's quake measuring 7.1 in magnitude.
Cooling operations have resumed following the aftershock and the operator still has an emergency back-up generator.