Rescuers have found 30 hikers in critical condition, feared dead, near the peak of Mount Ontake, after Saturday's sudden volcanic eruption, reports GHN based on BBC.
The hikers were not breathing and their hearts had stopped, reports said. Final confirmation of death in Japan always comes via a medical examination.
About 250 people were trapped on the slopes, but most have got down safely.
The volcano, about 200km (125 miles) west of Tokyo, erupted at about noon on Saturday, spewing ash and rocks.
Ordinarily it is a popular place to see autumn foliage.
Japan is one of the world's most seismically active nations but there have been no fatalities from volcanic eruptions since 1991, when 43 people died at Mount Unzen in the south-west.