A Mount Fuji disaster management council said Monday that pyroclastic flows could sever major roads in the instance of an eruption of Japan's tallest mountain, underscoring the need to review existing evacuation plans that use the roads.

In an interim report on a review of a Mount Fuji hazard map, the council forecast flows of hot gas and volcanic matter could travel some 4 kilometers further than previously thought in Fujiyoshida, Yamanashi Prefecture, and 2 km more in Fujinomiya, Shizuoka Prefecture, after it analyzed 35 locations with steep slopes.

The reassessment meant that parts of the Higashifujigoko toll road connecting Fujiyoshida and Shizuoka's Oyama, as well as the Mount Fuji Skyline road connecting Fujinomiya and Gotemba within Shizuoka, could be destroyed.