However, officials added a rise in radiation levels has been observed only in sea areas near the power plant site, Kyodo reported.
Plant operator Tokyo Electric Power Co. developed a plan to freeze soil around the reactor buildings to prevent further accumulation of toxic water.
Prime Minister Shinzo Abe has directed the government to use its resources to help the plant operator bring the situation under control, The New York Times reported.
"This is not an issue we can let Tepco take complete responsibility of," Abe told a group of cabinet ministers gathered to discuss the plant. "We must deal with this at the national level."
Abe called recent revelations of new contamination flowing into the Pacific Ocean an "urgent issue."
A "chemical wall" built in June has failed to contain the contaminated water, regulators said, and it now appears to be flowing over the top of the barrier and into the Pacific.