Japanese authorities were investigating a new possible radioactive leak at a nuclear plant hit by an earthquake in northern Japan, Kyodo News agency said.
Officials said a series of stacked drums containing low-level nuclear waste fell over during Monday's quake and some of the lids were found open, Kyodo said, citing officials in the city of Kashiwazaki, near the epicenter.
Another leak at the Kashiwazaki Kariwa nuclear power plant would sow further doubts about the safety of Japan's nuclear power plants, which have suffered a long string of accidents and cover-ups amid deep concerns they are vulnerable in earthquakes.
Monday's 6.8-magnitude quake triggered a small fire at an electrical transformer in the sprawling plant. But it was announced only 12 hours later that the temblor also caused a leak of water containing radioactive material.
Officials said the water leak was harmless and well below safety standards.
The Kashiwazaki Kariwa nuclear power plant, the world's largest in terms of power output capacity. Fifty-five reactors supply about 30 percent of Japan's electricity.