More than 30 people are reported dead after a volcano unexpectedly erupted in Japan Saturday.
Specific casualty numbers are hard to come by, since Japanese officials do not confirm deaths until after a doctor's formal examination.
But according to the BBC, officials say about 31 people were found dead of heart and lung failures on Mount Ontake, a popular hiking spot this time of year because of its autumn foliage.
Including the 31 discovered, 45 people remain unaccounted for Sunday. Workers were forced to suspend rescue efforts over fears of a toxic gas build up on the mountaintop.
Local officials estimate more than 250 people, mostly hikers, were on the mountain when it erupted. This video shows hikers hurrying down the mountain before being engulfed in the ash cloud, which covered the mountain in almost a foot of ash.
And now NHK reports officials are warning people to expect further eruptions on a similar scale.
Mount Ontake hasn't shown this much activity since 1991. But it has erupted like this before. Back in 1979, an eruption emitted 200,000 tons of ash
So, now many are wondering how no one saw an event of this size coming.
The New York Times reports that several minor earthquakes led up to the eruption but nothing to give seismologists any indication that a major incident was on its way.
But The Guardian quotes a professor of planetary sciences who says, "'Sneak' eruptions lacking in precursor signs are not unknown, but analysis of the records may reveal data that, with hindsight, should have been read as a warning sign."
Experts concluded that Saturday's eruption was a hydrovolcanic explosion caused by underground water suddenly turning to vapor after being heated by rising magma.
It is still not clear when officials plan to resume rescue efforts.
This video contains images from Getty Images.
