Waters leaks have been found at another nuclear power plant after a strong aftershock hit Japan on Wednesday but there has been no change in radiation levels outside the plant, according to its operator.
A powerful 7.1 magnitude earthquake on Thursday jolted the Miyagi prefecture on the northeast coast, the area devastated by a massive earthquake and tsunami in March.
At least three people were killed and more than 100 injured in the aftershock.
The quake struck at 11.32pm, 66km east of Sendai at a depth of 49km, the US Geological Survey said. It was the strongest of the aftershocks from the 9.0-magnitude quake on 11 March and shook buildings as far away as Tokyo.
The Tokyo Electric Power Company (Tepco) says water has leaked out of spent fuel pools of the Onagawa nuclear plant's No 1 and No 2 reactors and other parts of the plant, Reuters reports.
However, no new damage has been detected at the Fukushima Daiichi nuclear plant that has been crippled since March, Tepco says.
Thursday's quake cut power was been cut in three regions, and there have been reports of fire and minor damage, and some injuries.
Workers were evacuated from the Fukushima plant, the BBC reported, and Japanese authorities ordered a new evacuation from the warning zone.
The workers are trying to keep the damaged reactors cool to stop further releases of radioactive material.
A tsunami alert issued after the quake was cancelled after 90 minutes. Waves of up to 1 metre in height were recorded hitting the coast.