Japan’s nuclear power plants are at risk from “impossible to predict” volcanic eruptions, a prominent Japanese volcanologist said Friday, disputing findings of the country’s nuclear safety regulators. A panel of regulators had, in September, declared the Sendai nuclear power plant, which is located in southern Japan, as safe, and ruled out any eruption at the volcanoes surrounding the plant, according to media reports.

“It is simply impossible to predict an eruption over the next 30 to 40 years,” Toshitsugu Fujii, a professor at the University of Tokyo, heading a government-commissioned panel on volcanic eruption prediction, reportedly said.

“It has been much too quiet here over the last century, so we can reasonably expect that there will be a number of large eruptions in the near future… the 2011 quake convulsed all of underground Japan quite sharply, and due to that influence Japan's volcanoes may also become much more active,” Fujii reportedly said, referring to the earthquake and ensuing tsunami that killed thousands and caused a meltdown in the Fukushima Nuclear power plant.

He added that pyroclastic flow -- a hot, fast moving current of gas and sediments -- from Mount Sakurajima, an active volcano just 25 miles from the Sendai power plant, could easily hit the region, making it impossible to access the plant. This could, Fujii reportedly said, result in a catastrophic nuclear meltdown in the reactors at the plant.

“Scientifically, they're not safe… If they still need to be restarted despite uncertainties and risks that remain, it's for political reasons, not because they're safe,” Fujii reportedly said, adding that a number of other experts in the panel also disagreed with the findings of the regulator.

Fujii also said that Mount Fuji, which last erupted in 1707, could also erupt “at any time.”

“The last eruption was 300 years ago, ten times longer than before," Fujii reportedly said. “Fuji is showing absolutely no signs of eruption at this point… But that says nothing about next year.”